The Bay to Breakers is really two races: a screaming-fast elite 12K across the city to the ocean and a carnivalesque parade of 65,000 runners in various states of both costume and undress. If you're there to race, arrive at least an hour before the gun to slip into one of the new corrals for more serious runners near the starting line, so you won't have to slalom through the jogging mariachis, the human six-packs, and the infamous school of upstream-running salmon. Don't blow your reserves on the 11 percent climb up Hayes Street; save your breakaway for the top and the next 4.5 miles of gradual downhill through Golden Gate Park. If you're there to party, don't wear anything you'll regret after five miles (like a fat suit), and don't flaunt your fun. The cops won't return that ingenious kegmobile, full or empty. $44; ingbaytobreakers.com

THE SEVEN HABITS OF HIGHLY SUCCESSFUL RACERS

You've registered and bought the gear. Now make the most of your big day.

1. Train high, race low. Don't expect to be at your best if you're training at sea level and racing in the Rockies. But if that's what you have to do, make a vacation out of it and arrive a week early to acclimatize.
2. Pick the right team. Success will hinge on having everyone, from relay mates to support crew, working toward the same goals. Talk through your expectations before you commit, especially when large fees and travel are involved.
3. Give yourself enough time. Allow a full day to recover from travel before an important race, and get up early. Race-day mornings are always more complicated than they seem the night before.
4. Never try anything new on race day. Unless you like equipment failures, blisters, and Porta-Potty lines, save the experimentation for the post-race party.
5. Know the course. You can't pace yourself if you don't know what's in store.
6. Start slow. Everyone feels like a hero at the starting line; chill out so you can finish like one.
7. Eat early and often. Aim for at least two gel packets (50–60 grams of carbs) or the equivalent per hour of exertion—and enough electrolyte drinks so you never feel even close to thirsty.