One trick I have heard is to force yourself to develop a habit in your waking life where once every couple of hours you consciously asked yourself "Am I awake right now?", paired with something physical like looking at your hands or something. The idea is that if you develop this as a habit eventually you will do it in a dream, at which point you will realise you are dreaming.

Generally it seems that very light sleep, (like when you wake up in the morning but snooze the alarm and go back to sleep) is more conducive to lucid dreaming. Some people set alarms at intervals throughout the night to achieve this but that can be very destructive to sleep health.