Kids are master

For siblings who refuse to cooperate with each other, assign them a task that they can do as a team, like picking up the toys.

Who will get the bigger room? Who gets to name the cat? Have the kids bid for it with their chores or allowance.

Don't make threats that will make you suffer too. "Don't make me turn this car around!" Pick punishments that benefit you. "If you continue, we're going to Grandma's instead of the movies."

When your kids are in some trouble and crying bitterly, don't bail them out of trouble. It will reinforce bad behavior. Establish clear rules and meet out punishment when necessary.