Taping your thumbs can help make it easier to use your hook grip in weightlifting. It can also help to avoid blisters and torn skin. This video illustrates a way to tape your thumbs so that you can get a good grip and not hurt your thumb from improper taping.
Some lifters find that it can also help to tape some fingers between the joints for the same reason. When taping the fingers, I typically tear a strip of tape in half lengthwise. I then wrap the finger between the joint and the palm or between joints. This allows full mobility while protecting the fingers.