My Mother-in-law had a little trick that worked wonders for me....sit them on chairs, on opposite sides of the room and facing each other. They will make faces at each other but after awhile, it'll turn to giggles. It was at that point that she would let them go play again. It worked great with my kids too!
Something else that worked great for me, especially out in public places is to pick two points and make them run back and forth between them. I figured that they had so much energy to burn, I'd help them burn off a little of it. Of course, I always did this outside (usually picking two trees fairly close together so that the distance wasn't overly far) and kept the amount of time appropriate to the age and made sure we would all be in a safe place. (My parents did this to us kids when we were young and I hated it but it was effective)
In the car, I simply pulled off to the side of the road (again, somewhere safe) and made them get out of the car and sit on the sidewalk while I stood there with them. I only had to do this twice, after that simply slowing the car down along with asking if they wanted me to stop, would cause them to stop because they were embarrassed by having to sit in full public view with mom standing over them, arms crossed.
As they got older, I made them exersize rather than just running, push-ups, jumping jacks, etc. And if they tried arguing with me, well, that's a simple solution too. Simply don't. Speak in a firm clear voice, let them know you mean business and just let them know that you didn't ask for their comments, just do.
If they were fighting over a toy, it went on top of the fridge, problem solved. They'd get it back a week later. Eventually they learned to share because they didn't like their toys being taken away. As teens, I simply took the cords to their equipment so it either wouldn't play or couldn't be charged (kept them in my purse or car's glove box) as punishment.
I'm sure if you think about it, you'll find your own little clever ways to handle things that are appropriate to your kids. Good luck to you hun!