There is some great advice on this thread. I'd like to add a couple of things. The first is that it's important to know where your audio files are located. Before you end a session it would be a good idea to quickly sweep down the audio window (Apple 9) and make sure the audio files are where you expect them to be. Also, I'd make different projects for different versions of the same song. Another idea is to keep a little log of what you did with each session. I leave that in the project folder. Finally, if you're not going to mix the tracks yourself then I'd be careful to bounce the dry tracks as much as possible. Depending on your computer's resources and your workflow this can be a monumental task, especially if the project is a hot mess to begin with. And most important, back that thing up on a weekly basis.