The purpose of a serve return is to move your opponent out of center court. The most effective and safe way to do this is to return the serve with a ceiling ball.
If you can hit a return of serve at knee level, then try hitting a passing shot down the line, cross court, or wide angle. Lob serves can be returned with ceiling balls or they can be cut off after they cross the 5 ft encroachment line.
Other possible returns include z-balls and around-the-wall shots but are more difficult to execute.
Do not let your return of serve rebound off the back wall, and avoid the worst of all shots, the skip ball.