A few years ago, I read on a theater message board that people should have an audition book; that is, a binder where you write down (a new page for each) every show you audition for, the theater, the date, the director, the parts you read for (or sang for), the song you sang/the reading you gave, people you met at the audition, feedback, and the final result.
I keep it in a loose-leaf notebook, and I’ve found it to be pretty useful, especially for musicals in re: what songs work better than others, audition cuts, etc. If I’m cast I write the name of my character and what numbers I was in (in a musical).If I’m not cast…well, at least I auditioned! Auditioning practice is always good. It’s also useful to have names, places, etc. for when you re-audition for a company–you can refresh yourself on names, and you know what sort of reading/song to give, based on your previous experience.