Fix it sooner, not later. If your shoelace is getting untied, or you start to chafe early in the race, take care of it before it becomes a real problem later in the race.
Line up early. You don't want to be rushing to the starting line, so don't wait for the last call to get there.
Start slow, and stay even. Run the first 10 percent of the race slower than you normally would, with the idea that you'll finish strong. Don't try to "bank" time by going out faster than your goal pace. If you do that, you risk burning out early. Try to keep an even pace throughout the race, and save your extra energy for the final stretch to the finish.
More: Pacing Strategies for Every Race Distance
After the Race
Keep moving. Get your medal and keep walking for at least 10 minutes to fend off stiffness and gradually bring your heart rate back to its resting state. Be sure to do some of these post-race recovery stretches to stretch out your legs, back, and hips.
Refuel. There are usually snacks at the finish line, but what the race provides may not sit well with you. To recover quickly, bring a snack with a combination of protein to rebuild muscles and healthy carbs to restock your energy stores. Consume it within 30 minutes of finishing the race. You might try a sports recovery drink, energy bar, or other packaged food that won't spoil, spill, or get ruined in transit.
The 9 Golden Rules of Recovery
Get warm. Change out of the clothes you ran in, and get into dry clothes as soon as possible. After you cross the finish line, your core temperature will start to drop fast, and keeping sweaty clothes on will make you cold.
The next day, get going. As sore as you might feel the day after the race, it's important to do some sort of nonimpact activity like swimming, cycling, or working out on the elliptical trainer. The movement will increase circulation to your sore muscles and help you bounce back sooner. Just keep the effort level easy.