Better Luck Working with What Already Exists
I too, have had some difficulty "willing" something to occur. I also agree with the post that suggested closely examining the materials available, and it seems to solidify the dream and stabilize it.
I had a scary one the other day, though, where all images disappeared completely, and I was just lying on my bed in utter darkness but couldn't move (obviously still asleep).
It has actually happened a couple times since, and I have found spinning to be helpfuil.
The other day, I spun, and when I stopped, the building I was enclosed in now had one of its walls missing, leading to a beautiful lake. I decided to dive in to see what would happen when I went underwater.
It was exactly like being underwater. Very murky. Except that I found I could breathe.
As far as mirrors, the first time I saw a mirror while walking down a hallway, I floated over to it to see what I'd look like. I saw my own features, but distorted exactly like Alfred E. Newman from Mad Magazine. I actually laughed in the dream.