Samson, I have a question.  Where should I contact most of the balls – when the ball is rising, when the ball has reached the peak in the trajectory, or as the ball is falling?
 
 
 
Good question.  I’ll give a separate answer for each stroke.
 
When blocking, it is important to contact the ball on the rise; this will help you to keep your block low and give your opponent less time to react.
 

In table tennis, you can contact the ball on the rise, on the top of the bounce, or on the fall.  Sometimes beginners have difficulty controlling the spin, depth, and power because they don’t know when to hit the ball.