I generally ask my students to make several videos of themselves playing their recital piece in the weeks leading up to the performance. This accomplishes several things...
1. They always record it a number of times before selecting one to bring to their lesson. Repetitions are good!
2. They can hear the sound they are getting when not focused on the task at hand. In other words, as performers we often think it sounds a certain way or we're doing a great job of this or that. Sometimes in reality it's very different than our perception while playing!
3. We can silence the video and notice whether anything looks awry. For instance, are funny faces being made? Are we swaying back and forth like a snake charmer? Does our posture look good or is there room for improvement...?
Sometimes the best teacher we can have is a video recorder!