I've had lucid dreams for couple years time to time. It's a learnable skill which involves developing a state of mind where you are aware about the world around you and always questioning its nature. With enough practice the attitude follows with you into your dreams. Easiest way to develop such state of mind is doing reality checks when awake. With enough repetitions you start doing them in your dreams, most reliable one being the "breathing test" where you close your nostrils and try to breath through your nose. Awake, of course you can't do it, but in a dream you can breath no problem. It's a real "holy shit" -moment when you suddenly realize you can breath despite closing your airways!