Try Stephen Laberge's mnemonic induction of lucid dreaming (MILD) technique.
Set your alarm clock to wake you up 4 1/2, 6, or 7 1/2 hours after falling asleep.
When you are awakened by your alarm clock, try to remember the dream as much as possible.
When you think you have remembered as much as you can, return to your place of rest, imagining that you are in your previous dream, and becoming aware that you are dreaming. Say to yourself, "I will be aware that I'm dreaming," or something similar. Do this until you think that it has "sunk in." Then go to sleep.
If random thoughts pop up when you are trying to fall asleep, repeat the imagining, self-suggestion part, and try again. Don't worry if you think it's taking a long time. The longer it takes, the more likely it will 'sink in,' and the more likely you will have a lucid dream.
When you are awakened by your alarm clock, try to remember the dream as much as possible.
When you think you have remembered as much as you can, return to your place of rest, imagining that you are in your previous dream, and becoming aware that you are dreaming. Say to yourself, "I will be aware that I'm dreaming," or something similar. Do this until you think that it has "sunk in." Then go to sleep.
If random thoughts pop up when you are trying to fall asleep, repeat the imagining, self-suggestion part, and try again. Don't worry if you think it's taking a long time. The longer it takes, the more likely it will 'sink in,' and the more likely you will have a lucid dream.