I like the method in the book about focusing your attention on a particular thing and not judging it, just understanding what's happening. I use that a lot. Many people really don't observe themselves very well, and I've found that asking them to pay attention to how their shoulders feel during a forehand, for instance, allows them to better observe what they are actually doing with their body during the stroke.
It also pretty much eliminates giving do this or do that commands while they are practicing technique that they just saw demonstrated. Once they realize what is actually happening during their swing they already know what to change based on the initial instruction and demonstration of the technique.