I never recognize dreamsigns either. When I'm lucid, I know I'm lucid. When I'm not, there could be a parade of dreamsigns walking by and I won't notice it. Only once have I been in a dream, and spontaneously thought, "Hey, I should do an RC," and then got lucid from that.

Usually, I'll just be minding my own business, then suddenly, Hey, I'm dreaming! I think it has to do with our state of mind. Like when you're in the upper theta range, you'll get lucid no matter what. Maybe that's just another way of referring to your "dream energy."