A concious choice I made before starting Mass Effect 3 was that, unless I was dealing with my squad mates, I would be a complete jerk. I would only make "bad" or Renegade choices. This has really help me deal with the crippling aspect of Mass Effect 2 that I never really overcame: choice. I was always concerned with what would happen if I made the wrong choice. This time around I don't care because I decided ahead of time what I would do.
Also, I'm predicting that the "Promethean device" will eventually require Shepherd to act as the "catalyst" to wipe out the Reapers. Or the device won't just destroy the Reapers, it'll wipe out everything.