Ive been doing a method that's works most of the time. I wake myself after 5 to 6 hours of sleep. Then I go right back to bed and start counting each one of my breaths. When I get to 100 I start at 1 again. If you continue to do that until you start dreaming, you'll be doing it in your dream. In the dream you wonder why you're counting, and then you remember, and then you realize youre dreaming.