Eh, I don't know. I feel like a total n00b, but I put the game down for awhile so I pretty much forgot to play and now I'm having a really tough time. I'm playing as an infiltrator, but a friend recommended I restart as soldier.
Plus, for some reason I couldn't even afford to buy ANY new weapons and armors. I feel like I missed out on something the first couple hours in.
OK. Here's the easiest way to play the game I know:
Make sure Liara is on your squad at all times. Make sure her Singularity and Lift skills are high.
If you have the Fitness ability, level it up until you unlock the Immunity power. Use that during combat and no one can hurt you.
To level up, go to the pause menu, select Squad and voila.
To use powers, hold RB during combat and select which power you want to use.