I'm surprised no one has said anything about intention. If you set your intention before sleeping it will greatly improve your chances of becoming lucid. Think to yourself "I will lucid dream tonight" and put power into that thought. Try to turn that thought into a memory the same way you would intentionally remember where you put your car keys. Create a mental hook, make space for it in your mind and let it sink in. Know that tomorrow you will wake up having had a lucid dream because you set the intention. It's very similar to belief except in this case you are using your own willpower to make it happen.