Odd. I was going to say almost exactly the same things as Ozme. Even the positions I used to train my rose were very similar. Anyway, they're great suggestions, and I heartily recommend them.

One thing he touched on but didn't really take further is the idea of a mantra. This is basically a set phrase of a few lines that the sub can repeat to herself, either internally or alound. I try to create a statement that gives the sub both a place to feel secure, and a thing to aim for. A sort of combination identity and mission statement. It takes a while to have effect, but combined with the position training it can soon give your sub a shortcut switch into a happy, submissive state of mind.

This is particularly helpful if you combine it with making her recite it for you in odd situations, say while she's kissing your feet, being beaten or right on the edge of orgasm. Watching her try and get it out while struggling not to cum is always entertaining.

Hope these help.