A Fault is any violation of a rule. Here are other ways to make a fault:

It is a fault if she swings at and misses the ball.
It is a fault if she hits the ball into the net.
It is a fault if the ball hits the net post or any other permanent fixture, even if it bounces in the service court.
Susie must not STEP on or over the baseline before the racket hits the ball or it is called a Foot Fault..
She may STEP on or over the line after the racquet hits the ball.  
Tennis Pro Note:  Leaning over the line (without touching it during a serve is perfectly legal!)

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Let Service. If Susie serves a ball which hits the top of the net and then bounces into Sam's service court, it is called a let service. The let service is not a fault and doesn't count as one of their two tries. It's also a let service, if she hits the ball into Sam's service court before he is ready. You should not attempt to play a let service. If Susie tosses the ball and catches it without swinging at it, it doesn't count as a serve.  She can take it over. 

Alter the first point has been made, Susie serves from the left of the center mark for the second point. Now, she must hit the ball into Sam's left service court.  After the next point, she moves back to the right again. She is the server all through the game, alternating her position after each point is played.  As receiver, Sam may choose any position he wishes. He usually chooses to stand just between the side line and center mark.  If Sam tells Susie he's not ready but still attempts to return her service and fails, he is considered ready, and a point is scored against him. It's a point against Sam as a receiver, if he strikes Susie's service during her volley - that is before the ball has had a chance to bounce.  After the service, Sam or Susie can hit the ball either on the volley, or after a bounce.

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Now, here are the ways you can lose a point after service.
A point is lost by a player if he, his racket, or his clothing touch the net.
A point is lost by a player if he hits the ball more than once.
A point is lost by a player if the ball touches him or his clothing.
A point is lost by a player if he plays the ball before it passes over the net.
A point is lost by a player if he throws the racket at the ball and he hits it.
If a player hits a ball outside the court before it touches the ground, the ball is still in play.

A ball landing on a baseline or either sideline is good. The player in whose court the ball lands decides whether a ball is in or out.  If you have any doubt as to whether a ball is out or good, you must give your opponent the benefit of the doubt and play the ball as good.

If a player returns a ball which hits the top of the net and then lands in the proper court, the ball is good. A returned ball is good if it hits the net post and lands in the proper court.

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Tennis has its own scoring system. 

First Score - 15 Second Score - 30 Third Score - 40 Fourth Score - Game

First score is fifteen; second score is thirty; third score forty, and fourth score, game . . . except when the score is tied at forty.  The server always calls the score - and he always gives his own score first. LOVE in tennis means zero or nothing. When a score is tied you can say 15-15 or 15 all.

In tennis, when the score is tied at 40-40 it is called deuce. Now one player must win two points in succession to win the game. The person who wins the next point has the advantage.  It is called Advantage In if the server won the point, and Advantage Out if the person receiving the serve won the point. Regardless of who wins the first game the receiver becomes the server for the second game, and so on alternately after each game. Players change sides or after the first game and every other game after that. In other words, after every odd numbered game you change sides.  A set in tennis is a least 6 games. The person who wins the set must win 6 games and be at least two games ahead of the opponent. If two people are tied at 6-6 or have a game score of 6-5 they must play additional games until one person is two games ahead, as in the case of these scores 7-5, 6-8, 9-7, and so forth. A match in tennis is determined by the best two out of three sets.

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When two players play as partners against two others, the game is called Doubles. For Doubles play, the court is made wider by two additional areas called alleys These alleys make the playing area larger, but do not affect the service courts.  The order for service for doubles is as follows; If Susie serves the first game, her partner Sam serves the third game. On the other team Betty will serve the second game then her partner, Bill, serves the fourth game, and so forth, until they have completed a set.  The general rules for playing doubles are the same for playing singles with two additions; Partners may not hit the ball consecutively (meaning twice on the same side before the ball travels over the net) and it is a fault if a served ball touches the server's partner.

If you have any other questions regarding the rules of tennis, email to our pros at jay@tucsontennis.com!