Your shot selection depends on two basic criteria, the location of your opponent, and, the position of the ball. This means that you must always be aware of the court location of your opponent at all times.
If the ball is above waist height, then your options are limited to hitting a defensive ceiling ball. But if you can strike the ball at knee height, then a wider range of shots are possible, depending on the location of your opponent.
In general, you want to hit to the open court area. But this can be difficult if your opponent has claimed the prime center court position. The highest percentage shot is to hit a passing shot either cross court or down the line. You do not want to hit a passing shot too high or hard such that it will rebound off the back wall.
Other factors which may determine your shot selection include the speed of your opponent, your shot selection skills, and the current game score.
The safest shots to get your opponent out of center court are the cross court pass and the cross court ceiling ball.