Before you go to sleep, say to yourself, "I will awake from my dreams and remember them completely." Focus on your intent, do not let your mind waver. Repeat it over and over until you sleep. Then after a few hours (for me, about 4-5 hours), you'll wake up and your mind will be swarming with your memories. Be quick in writing them down, because they fade incredibly fast. But I've done this for a few nights in a row now (just learned about LDs about 4 days ago) and it hasn't failed to work.