S.H.
I love what Nikki said about "the look".....once you have control - that's all you need to do! My niece is working on her Masters in Education & swears that she references me regularly!
Watch the "1-2-3 Magic" video. It will teach you how to discipline your child.
Another trick is to not present the child with an opportunity to say "yes/no". Give them a choice: do you want milk or water? do you want me to put on the sunscreen or would you like to? In situations like this, the child is offered an opportunity to achieve autonomy. If he doesn't make the appropriate choice & instead chooses to act out....then it's off to time-out until he can speak/act like a big boy. Be consistent with this & you'll see rapid results!
& just as a heads-up, last week I did the 1-2-3 countdown to my 14yo! The other mom present was hysterical!