Graze, don't chow down. Rather than devouring a gigantic bowl of pasta the night before the race, which could upset your stomach, try eating carbs in small increments throughout the day before the race.
Put your hands on your bib. The night before the race, lay out your clothes, and if you have your bib, fasten it on. That's the one thing you need at the starting line. Don't show up without it!
On Race Day
Limit your sipping. Yes, you need to stay hydrated, but no major drinking 30 minutes before the gun; sip if your mouth is dry or it's particularly hot out. Some athletes will take a mouthful and use it as a rinse and spit. Your best bet is to stay hydrated throughout the day. Aim for half your body weight in ounces. So for instance, if you weigh 200 pounds, aim for 100 ounces of calorie-free fluids like water each day. If you weigh 160 pounds, aim for 80 ounces per day.
More: 4 Common Hydration Myths
Arrive early. Get to the race at least one hour before the start so you'll have time to pick up your number (if you don't already have it), use the porta potty, and warm up. You don't want to be running to the starting line.
Identify yourself. Put your name, address, cell phone number, bib number, and e-mail address clearly on your race bib, or better yet, use a RoadID, which you can wear on your wrist or shoe.
Bring a trash bag. A heavy-duty trash bag can provide a nice seat so you don't have to plop down on wet grass. If it's raining at the start, you can use the trash bag as a raincoat.
Bring extra tissue. The only thing worse than waiting in a long porta potty line is getting to the front and realizing that there's nothing to wipe with.
Don't overdress. It will probably be cool at the start, but don't wear more clothing than you need. Dress for 20 degrees warmer than it is outside. To stay warm at the start, you may want to bring (expendable) clothes that you can throw off after you warm up.
Set at least two goals. Set one goal for a perfect race and another as a backup in case it's hot, it's windy, or it's just not your day. If something makes your first goal impossible halfway through the race, you'll need another goal to motivate you to finish strong. And it's best to set a third goal that has nothing to do with your finishing time. This performance goal could be something like finishing, running up the hills rather than walking them, or eating the right foods at the right time and successfully avoiding GI distress!