What loses me a point during a rally?

Unless the rally is a let, you lose the point (Law 2.10) if you:

• fail to make a correct service or a correct return
• hit the ball and it touches anything other than the net assembly before your opponent strikes it
• hit the ball and it passes over your opponent's court or beyond their end line without touching their court
• hit the ball through the net, or between the net and the post, or between the net and the table
• obstruct the ball
• deliberately strike the ball more than once in succession
• hit the ball with a side of the racket whose covering does not meet the Laws
• move the table with your body or anything you wear or carry
• touch the net assembly with your body or anything you wear or carry
• touch the playing surface with your free hand
• in doubles, strike the ball out of turn

Touching the table with your racket hand, or leaning on it with your body, is not listed as a fault, provided you do not move it.