Well one thing you can do is look at your feet and then begin spinning, that usually changes the scene, but I don't know if it generally changes the theme of the dream (ie: happy, sad, nightmare, sexual, etc). One time when I tried to wake up by forcing my eyes open, I had a false awakening, then I tried it again and I woke up. Just a thought: One thing that I hear wakes most people up is some sort of intimate experience while in a dream state.