Lucid dreams, and vivid dreams in general, almost always occur during the REM stage of sleep. The first REM phase typically occurs ninety minutes after you first fall asleep, with additional phases roughly every ninety minutes afterward. The goal of this method is to wake up during a REM phase, then fall back asleep and continue the dream aware that you are dreaming. You won't be able to time your phases exactly unless you visit a sleep lab or have a very dedicated night owl watching your eyelids all night. More realistically, just keep repeating the method below until you catch yourself in REM phase. . There are many ways to increase the amount of REM sleep you get, as described in the linked article. One of the most effective, and the one that causes REM sleep to appear at regular times, is to stick to a daily sleep schedule and to sleep long enough that you wake up well-rested. This can be difficult to balance with the step below, which interrupts your sleep in the middle of the night. If you have trouble falling back asleep, try a different method instead, or limit your attempts to once or twice a week. Set one alarm to go off either 4.5, 6, or 7 hours after the time you fall asleep. You're more likely to be in REM sleep during these times, although it's difficult to predict in advance. The six or seven hour times are the most likely to work, because later REM phases last longer, and are more likely to contain vivid or lucid dreams. Write down your dream if you were having one, make yourself a snack, or just get up and walk around for a while. Your goal is to get your conscious mind active and alert, while your body is still full of sleep hormones. One study shows that staying awake for somewhere between 30 and 60 minutes gives the highest chance of a lucid dream. Close your eyes and fall asleep again. If you remember the dream you were having, recall it and fall back asleep, imagining yourself continuing the dream. Even if this takes quite a while to happen, you've got a decent chance at a lucid dream....

TL;DR in Vietnamese:
Bạn cần biết rằng giấc mơ có ý thức thường xuyên xảy ra. Khuyến khích cơ thể ngủ REM nhiều hơn. Thức dậy lúc nửa đêm. Hãy thức một lúc. Tập trung vào giấc mơ và ngủ lại. Thử những kỹ thuật tập trung khác.