My self-reviewing is fairly informal. I look over the games I've lost, browse through them and try to pin point some situations that I feel contributed to the outcome of the game. If there were fights, I look at them more closely and try to determine at which point I should have seen where it was going, and what I could have done differently. I also try to loosely identify decisive moves made by my opponent and I. I don't spend more than fifteen minutes on a self-review, though. (And I try to let a few hours or a day pass before I look at the games, to gain a bit distance.)
Occasionally I'll also use MFoG12, load up a game I lost, and then use the software's analysis tools. It is somewhat verbose about what it thinks of a move, what the expected continuation is and which alternative moves it would have taken a closer look at. It will also make blunt comments like, "I would never consider this move."

The main benefit of this is to think about moves (or even areas where to play) that I might otherwise not have pondered. It's probably a bit like having a stronger player to review games with.
I think actually sitting down and looking at your lost games is what really matters: the willingness to do it. The details of how exactly you do it may not be as important.
