Summarize the following:
The best time for a nap is between 12pm and 3pm, at which point your melatonin levels are highest and your energy level tends to be lowest. If you struggle with after-lunch drowsiness, grabbing a few minutes of nap can make you more productive and awake in the long-run, as opposed to gulping down an energy drink and trying to press on. Try to avoid naps after 4pm, especially if you struggle with insomnia. Sleeping too late in the day can make it harder to get to sleep at night, when you want to go to sleep. Grabbing 10-20 minutes of rest is usually best for a middle-of-the-day nap. More than that can leave you feeling drowsier than when you started, meaning you'll have to go through the whole waking-up process for the second time in the day. Alternatively, if you need a serious nap because you slept poorly the previous night, Try to aim for a full REM cycle of 90 minutes. Sleeping for 60 minutes can make you feel groggy for the rest of the day, whereas 90 minutes--a full sleep cycle--can leave you feeling refreshed. The idea of nodding off for too long can keep some people from actually falling asleep. Take the stress off and set an alarm, even if it's only 15 minutes from now, to wake you back up and get you back to whatever you've got to do. You can rest easy knowing you're not going to wake up when it's dark outside. Use your phone to set a quick alarm, or get a coworker to cover for you and knock on your door in 15 minutes. Then return the favor. While it may sound counterintuitive to drink a cup of coffee right before you go to sleep, caffeine's got to travel all the way through your digestive tract before you feel that caffeinated jolt--a process that takes about 20 minutes--so some pro nappers swear by the caffeine nap, which times itself perfectly with your wake-up. Down a quick cup of cold coffee just before nodding off and let the caffeine wake you up sharp and refreshed. It's still a good idea to set an alarm to keep yourself from sleeping too late.

Summary:
Nap in the early afternoon. Keep it short. Set an alarm. Try a caffeine nap.