Everything good on Craigslist is going to have a ton of competition, there's no way around it. Just keep your mind open to opportunities - I got my current place when my first choice fell through, but I asked the landlord if he had anything else nearby. Turns out one of his tenants in the same building wanted to move out early.

You might also consider living in Berkeley/Oakland - it's easy to get to SF via BART, and cheaper to boot.