Since so many plays nowadays involve some sort of ball-screen, choosing how you will defend it is a key to any successful defense. I think a lot of coaches at the HS level and lower teach a simple switch or fight through technique, and though they may work for most situations, they don't really put pressure on the offense, you are basically letting them run their offense. One of the best ways to surprise a team is to trap the ball-screen. I see it used a lot in college and the NBA but not at the HS level and lower. I'm not sure if it's because it is too difficult of a concept to grasp, but I think it can be very effective. Here, Kobe and the Lakers use it to surprise Manu Ginobili who is using a screen from Fabricio Oberto but gets trapped and loses the ball. Watch the video and read my thoughts below,

Though I don't think you can trap the ball-screen every single time, it is something that you can definitely use say out of a timeout, or right at the beginning of the game to get an easy turnover and to make the offense react.

Practicing the ball-screen trap:

This is relatively easy to simulate. It's simply a 2-on-2 situation with 2 guards and 2 forwards. The key to the ball-screen trap is communication. X4 has to communicate to X1 that he is coming out, X1 has to trail then trap hard.

One of the great things about this trap is that it happens far away from the basket. Even if Ginobili is able to make a pass, your players should be able to rotate and recover.

For an old video but a good one from one of my favorite coaches, Geno Auriemma's DVD on 8 essential defensive drills is a good one to look at for defensive ideas for your practice. As usual, check out the X's and O's Basketball forum to talk hoops and exchange notes.