I'm preparing using the tickets system with my son who will be 4 years old in 2 months. He is very defiant, so I would like his 1 misbehavior that we focus on first to be Doing What He's Told. But I'm not sure if that is still too vague considering his age. Sometimes that consists of ignoring me and sometimes it's flat out telling me no, and sometimes he says ok and starts to do it but then quits. He is a smart boy but I don't want to put too much on him too fast. Suggestions?