Sometimes, I'll try "building" a scene in my head, piece by piece. For instance, it might start with just a beach, and the ocean. Then, I'll put in some palm trees. Then, maybe a cruise ship off in the distance. Then, I'll focus on the sky, adding clouds, etc. This can be done with just about any scene you can imagine; a snowy field, a city street, the Grand Canyon. If my eyes are OPEN, however, I'll either focus on the ceiling, or the bottom of the pool if I'm doing a wet static. I once read that thinking in words isn't the best thing, as it makes the throat muscles tense up and try to form the words. So, I try to stay away from thinking words, even trying to phase out thoughts like "relax", and "you can do this". Trying to replace that with just a general, positive feeling. I have one of those overly-creative minds that tends to race along, so it's very hard to me to just black it all out. I'll have to work on focusing exercises to improve that.
Todd