Whether you're at work or trying to nod off quickly in your living room, your nap will be more restful and you'll be able to fall asleep more quickly if you make your environment dark. Close the shades, turn off the lights, and curl up somewhere comfortable. No lights, no radio, no TV, no distractions. If you're only going to lie down for 30 minutes, there should be a big to-do about easing yourself into slumber by listening to NPR for 15 minutes. Create total silence and get right into the nap. Hit the bathroom right before you take a nap. No sense in getting interrupted by nature 5 minutes into your break. If you have trouble getting to sleep quickly, consider playing some ambient drone music, white noise, or even turning on a fan to create a low-level hum that'll drown out the world. Do whatever will help you get into sleep-land that much quicker. ASMR videos on YouTube feature soothing up-close whispering or background noises that some people find sleep-inducing. It's an easy and free way to queue up something that'll help you drift off, or at least relax you. Try to lie down completely. Even if you're at work or somewhere other than your bedroom, lay on a couch, or even create a soft surface on the floor that you'll be able to recline on and grab a few Zs. It'll be too quick for you to get uncomfortable.  If you're at home, get into bed or lay on the couch. The couch can be a nice alternatively, because it'll be easier to get up and out of, making it seem less like a return to sleep and more like a quick break in your day. It'll be easier to get started doing things afterward if your nap is on the couch. If you're worried about getting in trouble at work, take your break in your car and put the seat back. If breaks are allowed, but napping at your desk is frowned upon, find somewhere private. Your body temperature drops off as you drift off to sleep, so Try to anticipate that you'll need a blanket or at least a long-sleeved shirt to stay warm enough to fall asleep. A nap isn't long enough to have to...

TL;DR in Vietnamese:
Tạo môi trường tối. Loại bỏ tiếng ồn và tác nhân gây xao nhãng. Xem xét việc sử dụng tiếng ồn trắng để loại bỏ tiếng ồn phiền nhiễu khác trong môi trường xung quanh. Nằm ngủ với tư thế thoải mái. Giữ ấm cơ thể. Nhắm mắt và hít thở sâu. Không nên cảm thấy có lỗi.