The modern game tends to emphasize power and pace on your shots. This is very evident on the serve where even the good club player can now hit a serve with enough speed to give the opponent trouble-if it goes in!
Being able to place your serve is a very underrated skill and can be the key to your success in the match. There are a few basic technique ideas that can help you hit the serve to your target.
First, pointing your racquet directly at the spot you would like the ball to land at the beginning of the service motion will line your shoulders up in a manner that will encourage the path of the swing to go towards your target. You can also vary the amount of your initial shoulder turn to get the ball to go more in the desired direction. Holding your shoulders sideways longer will also help keep the serve more to the right for right-handers and to the left for left-handers. Opening your shoulders earlier will move the ball in the direction of your front shoulder.
Finally, the last thought before you start the service motion should be to look directly at the target and imagine the ball traveling right to that spot.
Keep in mind that all of the things I just mentioned are dependent on the toss being consistently in the correct spot so that you do not have to adjust your swing to an errant toss.