1. Find a good place to nap.
2. Have caffeine right before you nap.
3. When you're close to finishing your coffee, set an alarm to go off in 15 minutes.
4. Outside of your office door, post up a sign that says you are power-napping and can be contacted at a certain time.
5. Get up as soon as the alarm goes off. Sleeping for any longer than 20 minutes will be counterproductive. Sleeping more than 30 minutes can lead to sleep inertia, making you feel sluggish and more tired than ever.