Mass Effect 2

- Vanguard has the best risk:reward and satisfaction but all classes are fun.

- If a class you pick feels limited in regards to weapon loadout, you can get an extra weapon type later on. Guns are good even on the power-focused classes.

- You may want to maximise either your Paragon or your Renegade score so you won't be unable to make the difficult checks that you don't know about yet. It's not as necessary as it was in ME1, but you'll still miss out on some things if you don't.

- There are some points where not doing an interrupt will resolve a situation differently.

- Purchase all of the upgrades for your ship, although the Medical upgrade isn't necessary. Get the planet-scanning upgrade ASAP, because scanning will be dull as shit and that upgrade makes it go slightly faster. Or, if you're on PC, you can just use a save editor to cheat your way to infinite resources.

- Your squadmembers have "loyalty missions" where they ask you to do stuff like save a family member, get revenge on someone who wronged them, etc. When you complete them (note that there's one or two missions where if you make the wrong choice you fail and they're not loyal), they gain a bonus power and they perform better in the final mission.

- The passive-buff skills are surprisingly good, especially Shepard's.

- When you start the IFF mission consider yourself locked into the approach towards the endgame.

- At one point you will have to choose someone to escort a group of people out of the area. For the best ending, you pretty much have to choose Mordin.

- You'll probably need a guide to execute the final mission "perfectly" and get the best ending, or you can keep the consequences of your own choices. You can always make a save before starting the final mission if you decide you don't like how it turned out.