How long have you been trying? For starters it's a good idea to work strictly on recall, which means whipping out the old pen and paper and keeping it by your bedside to write down key events that occur in every dream. You want to remember the dream in some length after waking up from each one, and recording them helps you do that. Get into that habit and you'll likely find inducing lucidity will be easier for you. Half of the work involves keeping your mind on the topic of dreams, which is why just saying out loud (before falling asleep) that you'll have a lucid dream is an effective aid.