I agree with these guys. Keep a dream journal... Everyday... It also helps to immerse yourself in the subject. Read articles about lucid dreaming, read others' dream journals. Above all, perform reality checks... All the time. The more you have lucid dreaming on your mind, the more likely you are to DILD. I perform reality checks A: whenever something strange happens. B: Whenever I think about it. I know that's kinda redundant, but it's really important to do them all the time.

Another note about Dream Journals: it really helps to write them in the present/infinitive tense. As in instead of writing "I walked outside my home, and I saw a frog on the sidewalk" Use "I'm walking outside my home and I see a frog down on the sidewalk." This not only seems to help recall, making the dream seem more real, but it seems (to me at least) that if you run over your dreams in your mind from the previous night as you're falling asleep, it helps you to have more vivid dreams that night as well.