Don't you ever wake up at all in the middle of the night? Sometimes a particularly weird or vivid dream will drive me out of sleep - and this is the best time to write that dream down. If you never wake up in the middle of the night, I agree with everyone else's suggestions (drink lots of water before bed, set your internal alarm to wake up, tell yourself repeatedly before you go to sleep that you will remember your dreams, or get an alarm clock to wake you up). There's not much to do besides these suggestions - and everyone creates their own techniques that work best for them. Everyone is different, therefore everyone must come up with their own unique ways of doing it. Good luck!