Why they do it: "Whining is an expression of discontent, whether it's boredom or hunger," says Norman E. Hoffman, Ph.D., author of Bad Children Can Happen to Good Parents. Plus, your preschooler has probably figured out that whining is an effective method for getting your attention, so it's his go-to voice when he's feeling upset or wants something.
How to deal: Even when the high-pitched whimpering has you reaching for your earplugs, it's important to keep your cool. Tell your child that you can't understand him when he whines, and that if he wants to talk to you he'll have to use a nicer voice. Then give him props when he does use a whine-free tone. Simply ignoring his howls won't help the situation and could make it worse; if you walk away from his caustic cries for a snack, just think how much crankier he'll be once dinner rolls around. And don't rule out fatigue; a whiny kid is often a tired kid.
Why they do it: Your kid may genuinely want to see what happens when she launches her sister's Barbie off the jungle gym, but preschoolers usually throw things during fits of anger or frustration or when they want to get your attention.
How to deal: Kids often don't realize their own strength and that the Frisbee they toss around in the backyard can do some serious damage when it's hurled across the dining room. So if you don't want to install bulletproof glass in front of your china, set up clear rules about what can be thrown (soft balls and pillows) and where (the yard and in bed). But if she's tossing books out of frustration, acknowledge how she feels: "I know you're mad, but you can ruin your books if you throw them. And if they get ruined, we can't read them. Once I get off this call we can read Curious George together."