According to WebTennis teacher Brent Abel (webtennis.com), you should think about your overhead by dividing your opponent’s court into thirds.
The Put-Away Overhead: If you are hitting a lob in the air that is very short – or letting it bounce and it is still very short – you are probably hitting DOWN on that ball to have it land in the front third of the court (nearest the net). It then bounces over your opponent’s head or is angled off the court for a winner.
The Approach Overhead: Hitting the ball into the middle third of the court, will probably have your opponents get their racquet on the next shot and return a weak reply or another lob, which you can then be more aggressive on.
The Defensive Overhead: You are pushed back and/or leaping for the lob; so you try just to get it back deep into the court and not give your opponents a sitter to attack, but something deep enough in the court to cause them some trouble. (Brent also points out that on this overhead you really need to think about snapping your wrist, or the ball will sail long).
Knowing where you are in the court can help you decide which is the right shot – and the right overhead – for the situation.