I played ME2 first .. since I had never heard of ME1 before ... and I liked it, so I decided to buy ME1 and do that and then replay ME2 with my ME1 character.
I was very annoyed at the game at the beginning, as I had trouble getting used to the difference in controls and way of playing (and the moronic AI of your companions).
Basically I try to do alot of sidequests before any of the "real" missions.
F.x. I did as much as I could at The Citadel before leaving, and then did several planet side quests before picking up T'soni.
Only real problem I have had was with Jax the arms dealer as my companions would get shredded in no time.
Now that I have better armor and higher levels, we seem to do much better, as the companions can last longer while standing around in the open.
So don't count too much on their help, but use them for distractions instead, so you have time to line up shots.
Also the smaller side missions you find on the various planets help you get used to the system and the controls, and learning what your companions can and (more importantly) can't do.
I still hate the controls, the AI and the fact that I have to remember where every planet I need to revisit is located .... and the fact that after "clearing" a planet, the Mako is still dropped in the same place, and you have to drive around to places you have already been.