I can't change my environment either. I've tried many times, and end up using too much concentration and wake myself up. But usually I find some sort of loophole. For example, if I am in a hotel or something I'll think, "As soon as I walk into the next room a *insert whatever you want* is going to be there."

Usually I write in my LDs, so in real life I have good ideas for novels and so such, so I will often wish for a desk to be in the next room, etc. Usually I have to picture the desk, with the pencils and paper, before I go into the next room and see it.

I hope this wasn't too ambiguous, and I hope it helps.