Can anyone please elaborate the rule for service in table tennis.
Is it necessary to serve cross table?
In doubles you must serve diagonally, but in singles you can serve in any direction.
The rules for service are in Section 2.06 of the ITTF Handbook:
2.06 THE SERVICE
2.06.01 Service shall start with the ball resting freely on the open palm of the server's stationary free hand.
2.06.02 The server shall then project the ball near vertically upwards, without imparting spin, so that it rises at least 16cm after leaving the palm of the free hand and then falls without touching anything before being struck.
2.06.03 As the ball is falling the server shall strike it so that it touches first his or her court and then, after passing over or around the net assembly, touches directly the receiver's court; in doubles, the ball shall touch successively the right half court of server and receiver.
2.06.04 From the start of service until it is struck, the ball shall be above the level of the playing surface and behind the server's end line, and it shall not be hidden from the receiver by the server or his or her doubles partner or by anything they wear or carry.
2.06.05 As soon as the ball has been projected, the server’s free arm and hand shall be removed from the space between the ball and the net. The space between the ball and the net is defined by the ball, the net and its indefinite upward extension.
2.06.06 It is the responsibility of the player to serve so that the umpire or the assistant umpire can be satisfied that he or she complies with the requirements of the Laws, and either may decide that a service is incorrect.
2.06.06.01 If either the umpire or the assistant umpire is not sure about the legality of a service he or she may, on the first occasion in a match, interrupt play and warn the server; but any subsequent service by that player or his or her doubles partner which is not clearly legal shall be considered incorrect.
2.06.07 Exceptionally, the umpire may relax the requirements for a correct service where he or she is satisfied that compliance is prevented by physical disability.
Scoring A match is played best 3 of 5 games (or 4/7 or 5/9). For each game, the first player to reach 11 points wins that game, however a game must be won by at least a two point margin. A point is scored after each ball is put into play (not just when the server wins the point as in volleyball).
The edges of the table are part of the legal table surface, but not the sides.
Flow of the Match Each player serves two points in a row and then switch server. However, if a score of 10-10 is reached in any game, then each server serves only one point and then the server is switched. After each game, the players switch side of the table. In the final game (ie 5th game), the players switch side again after either player reaches 5 points. Legal Service The ball must rest on an open hand palm. Then it must be tossed up at least 6 inches and struck so the ball first bounces on the server's side and then the opponent's side. If the serve is legal except that it touches the net, it is called a let serve. Let serves are not scored and are reserved.
Equipment The paddle should have a red and a black side. The ball should be either orange or white and 40 mm in size. The table should be 2.74 meters long, 1.525 m wide, and 0.76 m high.
Try this Link Also Official Rules