Lucid dreaming is where you realize in your dream that you’re dreaming. Anything that you can normally do in dreams, such as fly or shoot fireballs, you can do in a lucid dream, but you are an active participant deciding what to do.
The best thing you can do is to start a dream journal, which is fun even if you aren’t lucid dreaming.
Get a notebook and put it near your bed. When you wake up from a cool dream, write down the date and what you were dreaming about. Then you can read through it later and see what where some common signs that you were dreaming, such as breathing underwater or flying. Remember those signs so that when you notice them while dreaming you’ll become lucid.
The other thing to do is ask yourself throughout the day if you’re dreaming right now. One test is to expect your finger to go through your palm and then try to see if you actually can push it through. If you do this test enough, you’ll begin to do inside your dream and then you’ll become lucid.
There’s always more, but dream journaling and reality checks are the fundamental building blocks to having a lucid dream. You basically can’t have a lucid dream unless you’re doing those two things.