TRANSITIONS - THE 2 MINUTE WARNING
Always give your child a two minute warning when you are about to change venues. This gives the child time to bring closure to what he is doing. Imagine that you are at a cocktail party. You can't find anyone to talk at first, but you finally find someone incredibly interesting. Just as you are really getting into the conversation, your spouse comes up and says, "Let's go." You say, "Wait just a few minutes." But your spouse continues, "Come on, let's go now. You need to have a better attitude." How would you feel? That is how your child feels as well.
After the two minutes are up, say assertively to your child that it is time to leave. Don't repeat or nag.
If your child doesn't stop what they are doing when you ask them to, break down the task of stopping into smaller pieces. "Put your blocks down on the rug, stand up, turn around, and walk this way."
If they are not used to your following through, they might start yelling. Don't cave in. You can say, "I think you are wondering if you yell that you might be able to change my mind. I am not changing my mind." Then you firmly (while staying calm yourself) guide your child to the car.
As you are leaving, you could say, "Wow, it is tough leaving when you are having such a good time. We can play again tomorrow."