Prequel bonuses - Have a saved game file from the original Mass Effect on your hard drive, and use that profile in Mass Effect 2 to get the following bonuses:

100,000 credits: Mass Effect character with the "Rich" achievement
30,000 credits: Level 50 Mass Effect character
2,000 experience points: Level 50 Mass Effect character
5,000 of each resource: Level 50 Mass Effect character
50,000 credits: Level 60 Mass Effect character
4,000 experience points: Level 60 Mass Effect character
10,000 of each resource: Level 60 Mass Effect character

Dr. Pepper bonuses - Use the following steps to get the bonus Dr. Pepper bonus items. Go to http://www.drpepper.com/promotions/ea/signin/, and register for an account. Note: You can register three different accounts to redeem three different codes and get each bonus item. After creating an account, enter one of the following redemption codes, and select the "No Purchase" option:

CBEEAAA41NWH
CBEEAAAE4L9N
CBEEAAAFQG9J
CBEEAAAE98ZV

Select the "Redeem" button to get a login for an EA account. Log in with your EA account information that is linked to Mass Effect 2. Select Mass Effect 2 from the game list, and choose the desired bonus item. Repeat the steps with a new drpepper.com account to get the other bonus items.

Completion bonuses - Successfully complete the game. Then, start a new game with the cleared saved game file to start with the following bonuses: choose Loyalty Bonus Skill at the start; retain Skill Points from first playthrough; retain level and experience points from first playthrough; +25% experience bonus for all characters; 200,000 credits, 50,000 of each resource; Renegade and Paragon points reset to neutral; and your weapons and armor (but no upgrades) from first playthrough.

Loyalty mission bonuses - Successfully complete the indicated party member's Loyalty mission to unlock the corresponding skill for Shepard, alternate colors for their costumes, and increase the chance for surviving the suicide mission. Note: Successfully complete the Advanced Training research upgrade for your ship to be able to select the skills.

Armor Piercing Ammo: Archangel's Loyalty mission
Biotic Barrier: Jacob's Loyalty mission
Dominate: Kill Samara during her Loyalty mission, and have Morinth replace her.
Fortification: Grunt's Loyalty mission.
Geth Shield Boost: Legion's Loyalty mission
Inferno Grenade: Zaeed's Loyalty mission
Neural Shock: Mordin Solus's Loyalty mission
Reave: Samara's Loyalty mission
Shield Drain: Tali's Loyalty mission
Slam: Miranda's Loyalty mission
Warp Ammo: Jack's Loyalty mission

Extra Paragon and Renegade points - During conversations, look carefully for a prompt at the top left area of the screen. Quickly press LT when the wings appear for extra Paragon points. Quickly press RT when the star appears for extra Renegade points.

Easy max skills - Have at least four available skill points and a skill ready to be evolved to its fourth form. While evolving a skill from level 3 to level 4 at the squad menu, press A + X to regain all spent squad points and keep the skill evolution. This works best if you level a skill from 0 to 4 (10 points) at the same time. Repeat this process to fill every line of your and your crew's skill tree. -From: tigernipp

Easy Paragon and Renegade points - Throughout the game you will unlock training to redistribute your skill points. Talent Mastery adds a certain percentage to your Paragon/Renegade. Respec and distribute them into your Mastery repeatedly until your Paragon and Renegade are full.

Easy materials - To find some easy mining planets, go to the Micah system in the Vallhallan Threshold, and look for the three planets hidden in the asteroids. They are all "Rich" planets with a lot of materials on them to help with your upgrades. -From: Psychotic Elf

Easy skill points - Recruit Morinth to get the Dominate skill, and get a large amount of Element Zero. Buy the Advanced Training upgrade, and select Dominate. This will result in a bonus skill point, which is then used by the Retrain Powers upgrade. Repeat this process to get another skill point.

Quicker scanning for mining - While scanning a planet, do not hold LT. Instead, rapidly tap LT until you see a blip on the scanner. Then, go back over the area while holding LT to find the best location to send the probe.
Move the pointer to the left or right of the planet you want to scan. Press the Left Analog-stick and Right Analog-stick in the same direction to double the spin speed of the planet and allow you to locate resources on the grid line quickly.

Planet scanning - After scanning a planet and pressing Y, the planet information screen on the right reveals if the planet is "Rich", "Moderate", or "Poor". Rich planets give approximately 10+ good scan for ores. Ore yields vary from 1,500 to 3,000. Moderate planets give approximately 8+ good scans, but around 35% to 55% yield compared to rich planets. Poor planets give approximately 5+ scans with yields 5% to 25% compared to rich planets. Note: If there is an anomaly on the planet (typically a rich planet) and you land before you scan, usually the Star Map on the Normandy will put you in a strange location away from the anomaly planet. You must then go back and rescan to get your ores.

Cryo Bomb - This trick requires any Biotic that lifts your enemy off the ground and the Cryo Bomb tech. Use the Biotic to lift the enemy off the ground, then hit him or her with the Cryo Bomb while they are still under the Biotic's effect. This will cause him or her to be stuck in a permanent falling state, where they are not capable of causing any damage. This is very helpful when trying to prevent the deployment of Harbinger, as once he enters the glitched body he cannot move. Thus, you can kill him at the end of a fight to prevent him from jumping into another body.

Easy Geth Pulse Rifle - Change the difficulty to Hardcore before you land on the planet. Successfully complete Tali'Zora's recruitment mission to find the Geth Pulse Rifle in the room where you find Tali. You can then change the difficulty back to its original setting.

Rapid fire M-920 Cain - Shoot the M-920 Cain, and keep [Fire] held while pressing [Reload] after each shot. The shots will keep firing during the previous shots' explosions.

Getting Dominate ability and keeping Samara alive - Dominate is a very useful Biotic ability that allows you to control organic enemies and turn them into allies, similar to the Hack ability that controls synthetics. In order to get this ability as a Loyalty mission bonus to use for your character, you must help Morinth kill Samara during Samara's Loyalty mission. However, it is possible to keep Samara on your team but still get Morinth's Dominate ability by using the following trick. Play Samara's Loyalty mission up to the point where Samara confronts Morinth. Save the game immediately before the confrontation. When you must choose who to eliminate, choose the option that allows Morinth get the upper-hand on Samara and kill her. Create a separate saved game file. Go to the ship, and talk to Morinth. Load the previous saved game, then have Samara kill Morinth. You will now get to keep Samara as a squad mate and have Morinth's Dominate ability when you choose a bonus Loyalty power to add to your character in the prototype upgrade screen.

Romancing Yeoman Kelly Chambers - Talk with Yeoman Kelly Chambers often, and choose the kind responses. Invite her to dinner when you get the option. Do not let Kelly die during the final mission, and select a loyal escort for the crew in the final scene. After completing the game, talk to Kelly. You will get an e-mail from her. Go to your quarters, and invite her up using your console to get the romance scene.

Anomaly locations - Scan the indicated planets to find anomalies (side quests):

Nebula Cluster Planet
Caleston Rift Solveig Sinmara
Caleston Rift Talava Taitus
Crescent Nebula Lusarn Tarith
Crescent Nebula Zelene Helyme
Eagle Nebula Amun Neith
Eagle Nebula Strabo Jarrahe Station
Hades Nexus Sheol Gei Hin
HourGlass Nebula Faryar Daratar
HourGlass Nebula Ploitari Zanethu
Minos Wasteland Fortis Aequitas
Omega Nebula Ariniarkan MSV Strontium Mule
Omega Nebula Fathar Lorek
Pylos Nebula Dirada Canalus
Pylos Nebula Nariph MSV Broken Arrow
Rosetta Nebula Enoch Joab
The Shrike Nebula Xe Cha Zada Ban
Sigurd's Cradle Decoris Sanctum
Sigurd's Cradle Skepsis Franklin
Titan Nebula Haskins Capek

Element Zero locations - Search the indicated planets to find Element Zero:

Nebula Cluster Planet and amount
Calestone Rift Balor Caleston (moderate)
Crescent Nebula Lusam Tarith (rich)
Crescent Nebula Zelene Helyme (moderate)

Eagle Nebula Amun Anthur (rich)
Eagle Nebula Amun Sekhmet (moderate)
Eagle Nebula Relic Preying Mouth (rich)

Far Rim Dholen Gotha (moderate)

Hades Nexus Hekate Asteria (poor)
Hades Nexus Hekate Bothros (poor)
Hades Nexus Pamyat Dobrovolski (moderate)
Hades Nexus Sheol Gel Hinnom (moderate)
Hawking Eta Schwarzschild Etamis (rich)
Hourglass Nebula Faryar Daratar (rich)
Hourglass Nebula Osun Erinle (rich)
Hourglass Nebula Ploitari Thegan (moderate)

Krogan DMZ Nith Mantun (moderate)

Minos Wasteland Caestus Invictus (moderate)

Nubian Expanse Kalabasha Yamm (moderate)
Nubian Expanse Batalla Nearog (moderate)
Nubian Expanse Batalla Thunawanuro (rich)

Pylos Nebula Dirada Siano (moderate)
Pylos Nebula Satent Boro (rich)
Pylos Nebula Raisaris (rich)

Rosetta Nebula Alpha Draconis 2175 Aeia (moderate)
Rosetta Nebula Enoch Joab (rich)
Rosetta Nebula Enoch Laban (moderate)
Rosetta Nebula Enoch Mizraim (rich)

Shadow Sea Iera Prospect (poor)
Sigurd's Cradle Decoris Sanctum (moderate)
Sigurd's Cradle Skepsis Watson (rich)

The Phoenix Massing Salahiel Ekuna (moderate)
The Shrike Abyssal Urla Rast Talis Fia (moderate)
The Shrike Abyssal Xe Cha Tosal Nym (rich)
The Shrike Abyssal Xe Cha Zada Ban (rich)
Titan Nebula Haskins Capek (moderate)

Valhallan Threshold Micah Farlas (moderate)
Valhallan Threshold Micah Israfel (moderate)
Valhallan Threshold Micah Kakabel (moderate)
Valhallan Threshold Paz Garvug (rich)

Armor pieces - The following armor pieces will become available for purchase after certain points in the game:

Armor Sets

Blood Dragon Armor : +15% power damage, +10% shield strength; requires Dragon Age: Origins
Terminus Assault Armor: +10% storm speed, +15% shields, +1 weapons reserve ammo; requires pre-order bonus code
Inferno Armor: +10% negotiation bonus, +10% power damage, +10% storm speed by 10%; requires pre-order bonus code
Collector Armor: +10% regeneration, +10% storm speed, +20% health; requires Collector's Edition

Helmets

N7 Helmet: +5% health
N7 Breather Helmet: +5% health
Kuwashii Visor: +10% headshot damage; at Omega
Death Mask: +10% negotiation bonus; at Tuchanka
Umbra Visor: +5% power damage; requires linking Dr. Pepper bonus code to EA account
Recon Hood: +5% weapon damage; requires linking Dr. Pepper bonus code to EA account
Sentry Interface: +5% shield strength; requires linking Dr. Pepper bonus code to EA account

Shoulders

N7 Shoulder Guards: +3% weapon damage
Amplifier Plates : +5% power damage; at Illium
Strength Boost Pads: +25% melee damage; at Omega
Asymmetric Defense Layer: +5% health; at Tuchanka

Chest

N7 Chestplate: +5% power damage
Capacitor Chestplate : -10% shields regeneration delay; at Citadel, Illium, or Omega
Aegis Vest: +5% health; at Citadel
Shield Harness : +5% shields; at Tuchanka

Arms

N7 Gauntlets: +3% health
Heavy Damping Gauntlets: +5% shields ; at Tuchanka
Off-Hand Ammo Pack: +10% spare ammo capacity; at Citadel
Stabilization Gauntlets: +5% weapon damage; at Omega

Legs

N7 Greaves: +3% shield strength
Stimulator Conduits: +10% storm speed; at Omega
Life Support Webbing: +10% health; at Citadel
Ordinance Packs: +10% spare heavy weapon ammo; at Omega

See Legion dance - Go up to Legion in his quarters. Highlight him, but do not talk to him, and eventually he will do the "Robot" dance.

Bizarre dialog with Legion

1. Take Legion to the Citadel. Talk to Anderson and the customs officer.
2. Take Legion to the migrate fleet on Tali's Loyalty mission. Security will force you to remove him unless you can persuade them otherwise.
3. Take Legoin to recruit Tali. She will try to shoot him.

Amusing surveying responses - Go to the Local Cluster, and survey Uranus. Instead of the usual "Probe Launched" response, the voice will instead make Uranus jokes such as "Probing Uranus" or "Really Commander?"

Baldur's Gate series reference - Space Hamster is available on Illium. Once you go into your cabin and select him, he will come out and do the same "Squeek" that Boo did, who was Minsc's "Intergalactic Space Hamster" from Baldur's Gate and Baldur's Gate 2.

Easy "No One Left Behind" achievement - Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Missing in Action (5 points): Save your crew from an overwhelming attack.
Very Elusive (10 points): Return to active duty.
The Convict (10 points): Successfully recruit the biotic Convict.
The Krogan (10 points): Successfully recruit the krogan.
The Archangel (10 points): Successfully recruit Archangel.
The Professor (10 points): Successfully recruit the Professor.
The Quarian (10 points): Successfully recruit the quarian.
The Justicar (10 points): Successfully recruit the Justicar.
The Assassin (10 points): Successfully recruit the Assassin.
Friend or Foe (10 points): Obtain geth technology.
Colony Defense (25 points): Defend a human colony from attack.
The Prodigal (10 points): Gain the loyalty of the Cerberus Officer.
Ghost of the Father (10 points): Gain the loyalty of the Cerberus Operative.
Catharsis (10 points): Gain the loyalty of the biotic Convict.
Battlemaster (10 points): Gain the loyalty of the krogan.
Fade Away (10 points): Gain the loyalty of Archangel.
The Cure (10 points): Gain the loyalty of the Professor.
Treason (10 points): Gain the loyalty of the quarian.
Doppelganger (10 points): Help the Justicar resolve her mission.
Cat's in the Cradle (10 points): Gain the loyalty of the Assassin.
A House Divided (10 points): Hack a geth collective.
Ghost Ship (25 points): Complete the investigation of a derelict alien vessel.
Suicide Mission (50 points): Use the Omega 4 Relay.
Mission Accomplished (125 points): Save humanity throughout the galaxy from certain annihilation.
Against All Odds (15 points): Survive suicide mission.
Insanity (75 points): Complete the game on the "Insanity" difficulty level without changing the setting.
No One Left Behind (75 points): Keep your team alive through the suicide mission.
Long Service Medal (75 points): Complete Mass Effect 2 twice, or complete it once with a character imported from Mass Effect 1.
Paramour (50 points): Successfully pursue a relationship with a teammate.
Head Hunter (10 points): Perform 30 headshot kills with any weapon on humanoid targets.
Brawler (10 points): Shoot and kill 20 enemies while they're knocked back by a punch.
Big Game Hunter (10 points): Thresher Maw defeated.
Tactician (10 points): Hit 20 different targets with multiple biotic powers to combine the effects.
Master at Arms (15 points): Kill enemies with 5 different heavy weapons during the game.
Merciless (10 points): Make 20 enemies scream as they fall or are set on fire.
Overload Specialist (15 points): Disrupt the shields of 25 enemies.
Warp Specialist (15 points): Warp the barriers of 25 enemies.
Incineration Specialist (15 points): Incinerate the armor of 25 enemies.
Operative (15 points): Complete a mission discovered by scanning an unexplored world.
Agent (50 points): Complete 5 missions discovered by scanning unexplored worlds.
Prospector (5 points): Retrieve mineral resources by scanning and probing a planet in the galaxy map.
Explorer (10 points): Visit 100% of the planets in an unexplored cluster.
Power Gamer (10 points): Reach Level 30 with one character.
Scholar (15 points): Unlock 15 new Mass Effect 2 codex entries.
Technician (15 points): Obtain 10 technology upgrades.
Weapon Specialist (15 points): Fully upgrade a weapon.
Scientist (10 points): Complete any research project in the Normandy's laboratory.
Fashionista (5 points): Personalize your armor in your quarters on the Normandy.
Power Full (15 points): Evolve any power.
Highly Trained (15 points): View all advanced combat training videos at Shepard's private terminal.

The following achievement requires the "Zaeed" bonus downloadable content:

Revenge! (15 points): Gain the loyalty of the mercenary.