Over the past seven years I've gotten good at napping. By "good" I mean I can consistently fall asleep inside of two minutes and wake up 20 minutes later feeling refreshed. I've even developed the ability to nap in a desk chair in a room with music playing and people talking. Here's what's worked for me:

1. Seize the moment. It's important - particularly when you're just starting out -- to nap right when you start feeling drowsy. Your goal should be to go from whatever you're doing to asleep in as little time as possible. Environmental factors, like how far you are from your bed or sofa, make a difference. If you have to climb a flight of stairs to get there, you're likely to loose the "edge" of your drowsiness.

The most helpful thing for me is having a dedicated nap button on my alarm clock. I press one button and my alarm is set to go off in 20 minutes.

2. Build up gradually. I couldn't always nap sitting in a loud train car, I gradually built up to napping at this level. When I napped my first semester of college, I napped in my bed in my quiet dorm room with the lights off. Then I learned to nap easily with the lights on. Then in the library, with my head resting on the desk. Then on the hard linoleum floor of the computer lab. Then sitting on a noisy bus.

3. Don't nap too long. I've found my ideal nap time is 20 minutes. Less and I don't get REM sleep (I actually dream!); more and I wake up groggy rather than refreshed.

4. Figure out your natural time to nap. For me this is between 3 and 5pm, with the peak around 4pm. If I nap too late in the evening, it can disturb my normal sleep schedule. If I nap too early, I may have trouble falling asleep immediately.

5. Don't have shame. Like with many things, people avoid napping because they're embarrassed to do it, particularly at work. It makes you look lazy and unproductive. In reality, I've found it's a huge net productivity increase because my mind is so much more crisp after I nap. I've found that I feel better taking a daily power nap and shaving an hour off my nightly sleep than I do without the nap and sleeping for an extra hour.