Speaking as a local of San Diego and a prior Comic-Con attendee, I have a few tips:
Overall Items to bring: extra anti-body odor items, a decent amount of spending money, and a good night's sleep prior.
Food-wise, go outside of the Convention Centre and go a few blocks into Downtown, and you can find cheap food. That's what I'm gonna do, do it the local way!
Transportation-wise: Grab the trolley as early as possible, there's a special event track that goes all the way from State to the Convention Center, but it gets crowded. Fast. Plus it smells. If you're staying Downtown, then get up at the ass-crack of dawn (or earlier), grab coffee, and get there by foot, if you're close enough.
Also, meet up with other Escapists for fun, I'm trying to organize an Escapism Comic-Con, if they're enough interest.
Scratch that, I can't organize that, but someone send me a PM if you're willing to!