Taking the perfect nap

Pretty good visual and article from the WSJ:

Another trick to waking up perky after a short nap is to drink a cup of coffee before sleeping. Caffeine won't hurt such a short break and should lessen the effect of sleep inertia.

Dr. Dinges recommends sleeping partially upright to make it easier to wake up. Studies, he said, have found that not laying totally flat results in avoiding falling into a deeper sleep.

"A lot of people say, 'I only need four hours of sleep a night.' There's a few of them around but not very many," he said.