One of the least utilized methods for improving one's game, yet one of the easiest to do, is to study the way you play matches. What are your bread and butter shots? How do you win most of your points? What can you do to get these type of points to happen more often?
The other thing to look for is how you are losing most of your points on. Is it serve return, your loop against backspin, or what? If you start really being aware of your weaknesses you can begin to work on practice drills to improve them.
The other way to use videotape is to create a better mental image of your game. You may not know exactly what a stroke should look like, but most players have a general idea of what they should look like. If they see something on tape that is obviously wrong you can work on changing that technique. Once you have a better mental image of your game you can begin to realize more fully what your strengths and weaknesses are and begin to see what you must do to get to the next level.
The other reason to videotape your matches is to measure your progress. You may not have the rating improvement you hope for every tournament, but if you are looking more fluid and making better choices in matches your results will start to show that.