All it takes is a smile and a little energy in your face. And those things come from a sincere heart to connect with the child/children.
It helps to be able to perform some astonishing feat like a magic trick or a curious stunt. But those things aren’t necessary. If you find yourself in front of children and want to know what to do, just do what you did when you were a child.
More than anything, kids want to connect. They want to spend time with people who care and who want the best for them. It’s easier than you think.