It's like they said, mix up the angles. A good way to do this is practice whatever you're doing 10 times at one angle (unless it's an entire act!) and then 10 at another, 10 at another, do them with little pause in between too (finish the first time, take a deep breath and do it again).
I practice new sleights with two cameras at once (webcam and other cam) to get twice as much feedback (though the webcam quality isn't great) per session.
Camera's are also great for rehearsing scripts so you can know what it sounds like when you perform.