I loathe the form, and hate the idea of a sketch being called a play. But they are popular, and don't seem to be going away. Take a situation and find some interesting wrinkle -- conflict -- or surprise. An ironic twist. Think of Noel Coward's CAVALCADE, when the honeymoon couple stand mooning at one another on the deck of a ship, contemplating a rosy future, only to part and reveal a TITANIC life preserver. The O'Henry tag.
Or something that works for friends of mine: Write a 20, 30 or 40 minutes play, then separate the final ten minutes as a stand-alone. Sometimes, amazingly, it works. Audiences will be fascinated by what they don't know, and play catch-up. (Think how many times in acting classes that climactic scenes are more compelling.) Whatever you do, don't take the first ten minutes. Serve the old playwriting adage -- start as late in the story as you can.
"I'm a comedian, but in my spare time, things bother me." Garry Shandling