Q: How do you keep someone in suspense?
A: I’ll tell you tomorrow!

Explanation: Suspense is that feeling of wanting to know what is going to happen.  In his films, Alfred Hitchcock was a master of suspense, keeping you on the edge of your seat waiting to find out what was going to happen next.  That’s what makes this joke funny- the questioner keeps the listener in suspense by saying, “I’ll tell you tomorrow!”