If you’re into roleplaying, then you should really consider buying Play Unsafe by Graham Walmsley. It is chock-full of good techniques to use at the gaming table, drawn from improvisational theater. Some of them are amusingly Zen. Like, “Be obvious” or “Be boring”. Trust me, it’s good advice, especially when you see his explanations.
I’ve already found it helpful for A Flower for Mara, and I’ll probably reference it when writing the final manuscript.