The toss is the easiest to work on.
You don't even have to be on a tennis court. You can practice the toss by just tossing and letting it drop. When it bounces it should be about a foot in front and to the right of your front foot.
Just keep tossing and letting it bounce. You want to look at where the ball lands, but also you should be letting go of the ball at the top of the up swing of your tossing arm. The ball shouldn't be in flight more than a couple feet (unless you want a very high toss like Kiefer, or Graf). Hold your tossing arm up until the ball comes back down to get the feel of keeping that arm up, which is what you should do during a serve. Also, try to keep from imparting spin on the ball as you release it. Some toss it from their fingertips or from a 'C' created by the thumb and index finger to accomplish that.
Do that for as long as you have the patience to keep doing it. The toss is an extremely important part of the serve.
Another serve toss practice drill is to stand in front of a tall chain link, or forgving fence (a brick wall is not what you want here). Set up as if you are going to serve through the fence. Toss the ball and, with a normal serve motion and try to trap it against the fence with your serve motion. Try to use as normal a motion as possible. It's not easy as you don't want to do damage to your racquet. You are trying to establish how high your toss should be so that it's apex is right where the face of your racquet will be in your motion, and establishing the rythym of your motion.