Keep a dream journal.
This is perhaps the most important step towards lucid dreaming. Keep it close by your bed at night, and write in it immediately after waking. Or you can keep a recording device if you find it easier to repeat your dream out loud. This helps you recognize your common dream elements (people from your past, specific places, etc.), and also tells your brain that you are serious about remembering your dreams! It will also help you to recognize things that are unique to your dreams. You will be able to recognize your own "dream signs." These will be recurring things or events that you may notice in your dreams.