There's a new rule for staying hydrated while running: Drink for thirst, and no more. "Some runners guzzle water before the start of a race on the assumption that they can store extra water in their bodies and thereby minimize dehydration during the race," says Fitzgerald. That's a mistake. On race morning, be sure to drink to satisfy thirst and stop drinking 45 minutes before the gun goes off.
During the race, the same principles apply. If you're not thirsty, don't force it. You will have to stop for water along the course a few times, of course, especially if it's a hot or dry day, so practice drinking from a cup on the fly by entering a shorter race (a 10K or half marathon) a few weeks before and grabbing a cup at the water station.
When it comes to sports drinks, be sure to be familiar with the impact it has on your body. While it will give a little boost for some runners, others may experience intense gastrointestinal distress. If this is the case for you (and you need ample experience to know), try gel packets instead to get the carbs and electrolytes you'll need in the race.