Haven't had deja vu since I was a kid but it was usually triggered by the memory of a dream.
You should try recording your dreams. Keep a journal [or recorder] by your bed. The second you wake up write down anything you remember. At first it might just be a few little things like 'blue ball' but eventually you'll remember scenes. Smells, food, and events before sleep can effect a persons dreams and/or help them remember. Meditation can also help.
Some facts about dreams you should remember, we go through sleep cycles throughout the night, so as we sleep we tend to have about 5 dreams a night. When we wake up we remember them all as one. Also, most dream in black and white, only those who are skilled with controlling and remembering their dreams see colour. Once we wake we fill in the colours of the grass, sky, sun. When something sticks out like a 'red cape' its because it was the only part of your dream in colour. Just thought those facts might help somewhat.