I do it a lot, practically every night, but like sweet slumber I don't actually know how exactly. One thing you could try though is writing a special lucid dreaming journal, charting your efforts to become lucid in your dreams. Even if it doesn't happen you can write that you were thinking about it before you went to sleep, then write down whatever dreams you had when you wake up and if you think you were lucid in any or not. If you keep doing this over and again it might just tell your brain that it's important to you, which might make it happen.