Say, for example, you are playing darts or throwing a baseball- how
do you aim?
Much of the aiming process is
1. Having a good, repeatable technique.
2. Developing a "feel" that you (unconsciously?) adjust- in increments
until your physical motion and mental image begin to synchronize.
But there are some basic things you can do/try.
1. Hold up the racket in the position where it would strike the ball
so that the racket face is like a mirror reflecting your target/placement point.
Adjust your Continental grip so your wrist flexes naturally toward that target
(like waving bye-bye). Now, your service motion should bring your racket face
to this position and the rest involves adjustments in basic motion, timing and follow-through.
2. As you strike through the ball realize that the forces affecting the balls flight
are no different than controlling the direction and spin of a forehand. The rackets
path through the ball will determine its flight.
3. Get some baseballs and, standing behind the service line, throw the balls
alternately to different markers (towels?) or placement points to get the feel of
controlling the ball by altering the service/throwing motion.
4. Practice.