Look, I watch tourists make the same SF mistakes every trip. Don't rent a car unless you enjoy hunting for $20/hour parking and navigating 31% grade hills on 22nd Street. Don't eat at most Pier 39 restaurants unless you enjoy overpriced mediocrity — Though Swan Oyster Depot (1517 Polk Street) and Ferry Building vendors exist for those seeking quality seafood at reasonable prices.

Here's the thing: don't pack light clothes because 'it's California' — SF summer brings thick fog that rolls over the Golden Gate Bridge by 11 AM daily, making it feel like Seattle. Don't plan Napa Valley as a day trip unless you want to spend 4 hours stuck on Highway 101 during rush hour. Don't expect everything to be walking distance — Those hills between Fisherman's Wharf and Union Square will destroy your ankles.

Don't assume BART runs late — Last trains leave downtown around 12:30 AM weekdays, later weekends. Don't visit Lombard Street expecting a peaceful photo — Tour buses jam the Russian Hill curves all day. Hit it before 9 AM or skip it for better views from Coit Tower ($11, Telegraph Hill).