A good serve starts with a good toss.
Here are some tips to ensure optimal contact during a tennis serve:

•    Cushion the tennis ball with your fingers.
•    Imagine you have an egg in your hand. Hold the ball very gently.
•    Keep your tossing arm relaxed.
•    Release the tennis ball above eye level.
•    Let the ball go up in a smooth, continuous motion.
•    Impart very little spin on it as it goes up. To do so, open your palm and spread your fingers as you let go of the ball.
•    The tossing height should be approximately as high as you can reach with the tip of your racquet.