The serve is widely regarded as the most important shot in tennis because it is the shot that begins every single point and it is the only shot in which you are in complete control of the ball, since it is in your hand.
Too many people are reluctant to work on their serves. They think it is boring because there is no running around and resist to put the work that is necessary sometimes to make changes. It is not rare that I hear people at Balboa Tennis Club, and everywhere else for that matter, saying that using part of a lesson or clinic to work on serves is a waste of time. This could not be further away from the truth and they are simply underestimating the importance of this shot.
Having a good serve allows you not only you put pressure on your opponent but also to play looser on your return games, knowing you can rely on it to hold your service games. Remember, serving well raises the overall level of your game and builds your confidence.
If your goal is to become a better, more complete player and take your game to the next level you need to learn all 3 types of serve -- Flat, Slice and Kick -- so you can have a variation of power, spin and placement on both first and second serves.
In the Flat Serve the toss is out in front and the ball is hit squarely from behind.
In the Slice Serve the toss is also out in front but slightly to the right for right handers and slightly to the left for lefties. The strings brush around the right side of the ball if you are right handed and around the left side of the ball if you are left handed.
In the Kick Serve the toss is above the head and slightly to the left for right handers and slightly to the right for left handers. The strings brush up behind the ball and from left to right for right handed players and from right to left for lefties.
The serve is the only shot in tennis in which you are in complete control. Your opponent can't do anything to keep you from serving well. There is no reason for you not to take it seriously and to not develop it as an asset rather than a liability for your game.