i second barbizzle's suggestion. do a reality check everytime you find yourself viewing things from the third person. the fact that you're even viewing things this way (if you're actually in a dream) could be an excellent trigger for lucidity.

also, try to 'possess' your body when you find yourself looking at a scene this way, and then look at your watch in the first person. i realize this could be tricky, but its helped me when my mind starts leaning towards third person perception. it helps if you imagine your third person awareness is a camera, and you 'zoom in'