It can be quite hard to get kids to clean their room. It depends on things like their age and personallity to get the perfect method, but here are some for younger and older kids.
-Make a clean...
You can get your child to clean his/her room by offering prizes. Or, take away the things that your child likes most. But the first answer was good enough, it's less harsh. But if offering your child...
You say to them that if they don't clean it that the monster in their closet would try to take them away. If they don't believe it say that you will take away their fav toy away for 1 week.