Repetition

As I work on my latest book, I've become increasingly frustrated with one thing: the repetition. I'm pretty sure every writer has this problem, but right now I feel like the worst writer in the world. My poor characters. They're stuck turning and saying and frowning, over and over again.

It's ironic; the English language is abundant. There are dozens of synonyms for just one word. Why, then, can't I seem to stop myself from using the same ones?

My technique is strict, if I do say so myself. Once I realize that I'm overusing a certain word, turn, for example, I won't let myself use it again. For the rest of the novel. Then as I go through it later, I'll deem it okay to use in certain places. And that's it. That's all I have to offer for this week. I'm quite consumed with bashing this habit down with a crowbar, so I really do need to get back to it.

What are your methods to avoid turning and saying and frowning a million times?