If you are playing ping pong at home with just a few of your friends, you probably have some pretty simple table tennis rules that you set up, rules that are oftentimes broken in the heat of the moment and that go unnoticed. This is fine for simple house games amongst family and friends, but if you are going to start playing competitively, you need to know the proper rules of the game. They are simple to learn, and once you start using them, it might be a good idea to get all of the other people with whom you play to follow these rules as well.
One of the most important rules and one that you will want to learn and adhere to right away is that you are not supposed to touch the table. When someone touches the table, they lose a point. People who are new to playing will sometimes touch the table without thinking about it, but failing to adhere to table tennis rules such as this will cost you dearly in a competitive game. By learning to keep your hands away from the table now, you won't have to worry when you are playing an important game.
Scoring is important as well. The first player who reaches 11 points is the winner of a game, and each match will have 5 games in regulation play. Determining the winner of the match is simple. The person who has the most wins out of those five games is the winner. Players switch sides after a game.
Serving is important as well. You need to make sure that the ball doesn't spin when you toss it up for the serve, and it needs to be tossed upward at least 6 inches.
When you are playing competitively, you will have two minutes to warm up before you begin playing. Use this time to loosen your body and get your mindset in the game. It's always a good idea to make sure that you know about the rules for any specific league that you might join. While many of them use the standard Olympic rules, you might find some that have alternate table tennis rules. Always follow the rules of your league, even when they differ from your normal house rules.
The rules of table tennis are simple, and once you know them, you aren't going to forget them.