Mass Effect 2

General

• 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.

• The game will refill your heavy weapons ammo to capacity fairly often, so use a heavy weapon at least once per mission, and try each at least a few times.

• 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 from Miranda 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.

• Your level cap is 30 (though you probably won't hit it without using an import character + DLC). That means that your teammates will have, at most, exactly enough skill points to max out 3 out of 4 powers - or mix and match, but be aware of the limitations.

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

• After completing the IFF mission, you have one chance to talk to your new squadmate and do his loyalty mission. Don't touch the star map before you do so if you don't want to get locked into 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.

DLC

• There's a fair bit of free DLC if you're on Origin.

• Genesis is good if you don't want to play through ME1 before starting a new character. Without it, the default options for what happened in ME1 are kind of shitty.

• The crewmember DLCs are fun. Zaeed's is free, so there's no reason not to download it, and Kasumi's is good, too, but you won't miss it if you don't get it.

• Lair of the Shadow Broker and The Arrival are each just one long mission. Broker is worth it if you care about Liara, but probably not if you don't. The Arrival acts as a sort of epilogue for ME2, and sets up some events in ME3, but it's fairly lackluster. If you get it, it makes the most sense to play it after the final mission.

• The equipment DLC gear is amazingly overpowered.