It's simple: auto-suggestion.

One habit that I want to start for ages is to spread lucid dreaming encouragements all over my room. Pictures of lucid dreaming art; get movie scenes (like matrix) and watch those during my WBTBs. Also, reading fantasy books like LOTR and eragon (eragon is epic cause it gives you tips about dream control I tell you!). If you fill your brain with this kind of stuff, you'll:

- feel inspired to have your lucid dream and to take your own adventures;
- stick this "fantasy" world into your memory and go to bed with a more fresh imagination (especially if you watch/read these "heroic" scenes during WBTBs!)

Good luck