Get a good night's sleep, and plan around your body clock so you drive at the times of the day when you are most alert.
Take a 10- to 15-minute break to exercise, stretch or walk briskly after every 2 hours you drive.
Let someone else do a share of the driving. Divide the driving into blocks of no more than about 4 hours for each driver.
Eat regularly to keep blood-sugar levels even, but be mindful of what you eat. A candy bar won't help much once the initial sugar buzz wears off. To stay alert, the body requires good nutrition.
Drink coffee or tea (or another form of caffeine) for a temporary fix. Keep in mind that caffeine does not take the place of adequate sleep.
Don't drink alcohol.
Avoid medicines that make you drowsy, including antihistamines, some antidepressants, cold and cough medications, and some prescription medicines. If the label warns, "Do not operate heavy machinery," you are being warned not to drive a car.
Learn to recognize drowsiness. Among the signs: You keep yawning, your head nods, your mind wanders, you feel eyestrain, or your eyes want to close or have trouble staying focused. It all means that you need a break from driving.
Take a nap if you're sleepy, even if you can't get to a bed. You'll have to judge your surroundings, but you're probably safer napping for a half-hour in a locked car pulled over to the side of the road than you are driving drowsy.