It makes me happy that your eventual first playthrough as femshep will be renegade. Renegade femshep is best shep, with better voice acting and a more interesting story.

For ME2, I'm gonna put behind spoilers the point you want to save until everything else is finished. The game isn't exactly on rails after that, but you'll want to go through the next parts immediately afterwards or bad things happen.

ME2 trigger pointAcquiring the Reaper IFF. Do everything else you want to finish in the game before doing this mission.