Allow and encourage making a mess.
This goes along with my previous post on failure. If things are getting messy, your child is making something and (hopefully) having some fun. Now I'm not advocating paste smeared on the walls and play-doh stuck in the dog's fur, but when the creative juices start flowing things can get a little messy. If art is so regimented and neat-nick that there's no room for error, then there's not really much room for fun either.
