Just tell yourself as you're falling asleep that you want to remember your dreams. And then first thing when you wake up, grab on to whatever dream you remember before it slips away. You can do this by writing in a notebook or dictating your dream into your phone. If for some reason you don't want to keep a dream journal, at least just take the moment when you first wake up to notice what you were dreaming and think about whether it has potential relevance to important things in your waking life. Pay close attention to any symbols or images you remember. This is really about figuring out what the symbols in the dream mean to you.