When my son was in preschool, I read an article about one house rule that covers all other house rules on the face of this earth. I adapted that rule in our own house.
That's the one and only one rule in our house.
No hurting yourself, others and the things around you.
This one rule in our home didn't confuse RJ when he was still a little boy. Very easy for a preschooler to remember. Up to now, same rule is still followed in our house.