Mass Effect 2

Do not play Miranda's loyalty mission at first. Instead, wait for Jack's mission to become available and play it first. After the mission when they are fighting, support Jack. Miranda's loyalty will be low. Then, play her loyalty mission to get it back.

Move the pointer to the left or the 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. This allows you to locate resources on the grid line quickly.

The game shop at The Citadel is a reference to a GameStop store.

Travel with Tali and Garrus, the recurring party members. Eventually they will have a conversation about the elevators. Garrus will fondly remember the interesting conservations they had about Quarrians. Tali gets very upset about to the point of threatening Garrus with her shotgun to stop.

Switch to the Hardcore difficulty setting before you land on the planet. 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.

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 the latter's loyalty mission. However, if you wish to keep Samara on your team but still have Morinth's Dominate ability, use the following trick. Play Samara's loyalty mission up to the point where Samara confronts Moritnth. Save the game immediately before the confrontation. When it is time to choose who you will eliminate, choose the option that lets 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 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.

Wander around the ship in between missions to hear some funny quotes.

Stand next to Jeff "Joker" Moreau (the pilot) without interacting with him. You will hear him say things such as the following.
"Why is it always claws and guns? Can't we piss off a fuzzy planet? Still dangerous, I know. But hey, bunnies."
"Two years and everything hits the crapper. That'll teach you to die on me."
"You know what I hate about deep space? Crap radio stations from two centuries back. My gosh, we were idiots."

Stand near the two engineers near the Mass Effect Core to hear the the following.
Engineer Daniels: "Did you know we're sharing our deck with a krogan?"
Engineer Donnelly: "Well that's just peachy."

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

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

Successfully complete a party member's Loyalty mission to unlock their individuals skills for Shepard, alternate costumes, and increase the chance for surviving the suicide mission. Note: 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.