Here goes the answers to your questions.

1. Look at the stroke your opponent is going to make. As soon as he makes the stroke, you have to watch the trajectory of the ball, the speed and spin. From that you have to make a judgement whether or not the ball is going to be short or long.

2. Position yourself well against the ball. Get into a practice session with your partner where you practice upward movement of your forearms against chops. After a while, the short will come automaticall to you. To learn how to Loop against underspin, I recommend a video called forehand Loop Mastery. This is a very good DVD and is available at http://www.TableTennisNetwork.com. The video can be purchased from the TableTennisNetwork.com site also.

3. Physical fitness is a must for a table tennis p_layer_. Before you play, take some warm up exercises.

4. If you are a beginner or intermediate p_layer_ to table tennis, dont use speed glue. If you are using regular glue, there is no need to change the rubbers unless it peels off or have bubbles.

Good luck.