Re: how to stop my 4 year old from peeing on things
How do you react when he does this, and who ends up cleaning up the mess?
First thing you need to do, before he pees on the floor again, is have a nice graphic chat with him about it. Tell him it's a choice that he makes. Have a brief discussion about how all choices have consequences or rewards. Then talk about all the germs that hide in poop and pee. Discuss the diseases that can be carried with those germs and the effects those diseases can have on people. Go to google images and show him pictures of people who've suffered from such diseases. Tell him the consequence of choosing to pee and poop on the floor is that HE gets to clean it all up from now on, and that if he can't show respect to his things, then you'll take them away from him.
Then when he does it again (and he will, because he will be testing you), be extremely calm and matter of fact about it. "Oh, you chose to pee on the floor? Okay, go clean it up." Show no emotion, and don't let him know he's messed up your day.
Make sure to continue telling him it was his choice and make sure he cleans it up by himself (obviously you'll have to go behind him and actually clean it, but don't let him know that! Let him think he's doing it all himself). Then after he cleans up whatever he messed up, take it away from him. His blanket, his toys, his clothes.... whatever he poops or pees on.
To get him to go in the potty, create a reward chart for him and put a sticker on it every time he chooses to use the potty. He can choose to earn back the things he messes up with a certain number of stickers (rewards!).