If you have a TV Tuner card in your PC, the bundled software (or ChrisTV, Windows Movie Maker) will easily let you take screenshots of any TV show frame. But if you want to shoot your TV with a camera, you have to do it very slowly as Dave Johnson explains- you need to use a shutter speed of less than 1/30 second.
The easiest way to do that is to set your camera to its shutter priority mode (usually indicated by an "S") and use the camera controls to change the shutter speed until you see a speed of 1/15, 1/20, or 1/25 in the viewfinder.
What if your camera doesn't have a shutter priority mode? Well, try the program mode. Usually, you can shift the shutter speed up or down by using the camera's controls--the aperture setting will change as well, ensuring that the exposure stays correct. Another alternative is to see if your camera offers a slow-shutter scene mode.
Source: Take Pictures of Images on Your TV