Not only should you talk, but strip it down to the bare bones. Remember, what's second nature to you isn't to the guy or gal sitting in the left seat who is looking for you to teach them. Tell them what to do, what to look for, where to be looking for it, when to be looking for it, how it should look, how it shouldn't look. That was my biggest challenge. Sure, you're doing turns about a point, but what are you doing to make those turns? The student is in the dark, they have no idea.

Don't be afraid to let your students make mistakes. Just don't let the mistake get you into a dangerous situation. Step in right before it gets to that point. Let them screw up the radios, let them get lost (with you in the plane). You get the idea.