Suck Up to a Blogger
Every major city has bloggers who are obsessed with what's new and great in their backyard, particularly in regard to restaurants. You can use Google Blog Search to find bloggers in whatever city you're visiting. They're a phenomenal resource, but don't just read what they're writing: Contact them for personal recommendations. The more specific your request — and the more you flatter them for their insight and wit — the more likely you'll be to pique their interest and get a response. ("What's your favorite vegetarian-friendly restaurant within walking distance of the InterContinental Hotel on Howard Street? We're looking for a place with a romantic vibe, ideally, because it's our anniversary. We'd be so grateful for your help, because you obviously know what's going on in San Francisco!")