The choices/decisions have huge impact on the future of your character, and the whole team, how you are percieved and treated, but I say, go with the decision you would really make in ME1, and you will experience further entries to be aligned to yourself. Without any spoilers, it's hard to say anything specific.

Some hints: who lives or dies, or who you spare, what you "destroy", who you get close with, every decision has consequences, and it might bite you in the ass in the long run. That's the beauty of this trilogy.

Prepare for replays with different approaches, it is well worth it.