First, start in your bedroom about ten minutes before it is time to turn in. You really do not have to worry about clown attacks during the day. Clowns tend to be nocturnal, preferring the cool night air to the hot sun. It melts their make-up. Second, spread random things all over your floor.
Clowns have really big feet.
If you spread enough stuff on the floor, you can hear them sneaking up on you. I like to use things with wires. On rare occasions you might even trip one, but don t bet on it. Clowns are surprisingly agile. Computer speakers, lamps, radios, and small televisions are all nice items to spread around.