Wake Back to Bed, or WBTB, is a method that can be used to try and increase your chances of having a lucid dream. To do WBTB, you simply need to wake yourself up in the night (typically 4.5 hours in), spend about 30-60 minutes awake and immersing yourself in dream-related activities (e.g. read your dream journal, read a book about lucid dreams), and then go back to sleep. This may increase your chances of having a lucid dream, because after 4.5 hours of sleep you should be going straight back into REM sleep when you go back to bed, which is the stage of sleep most associated with vivid dreams and with lucid dreams.
You can achieve the same effect by snoozing, though, so if you don’t want to interrupt a night’s sleep in this way, try setting an alarm and then letting yourself snooze a few times.