Pick the right partner
Before you commit, be sure the other parent shares your views on safety. Does she talk on her cell phone while driving? Will she make sure her charges are always buckled in?
Coordinate details beforehand
Discuss the little things (Is it all right to honk your horn at her house? Does she mind taking an additional passenger if you schedule a playdate after school?) and the big issues (Whom should you contact in an emergency? Do you have enough booster seats?). If your families don't know one another well, schedule a get-together now so the kids can get comfortable with everyone.
Prepare your youngster
Explain exactly how a carpool works and what's expected of her. Stress that when she's riding in the other car, she should always be buckled in and mind the other parent.
Lay down the law
On the first day you drive, spell out your road rules. Ask each child to look you in the eye and repeat them back to you, one by one.
Be ready with distractions.
The best way to head off backseat battles: Keep the kids busy. You might start a round of I Spy, tell stories, or sing songs.
Nip problems in the bud
When you're driving and a verbal warning doesn't put a stop to bad behavior, pull the car over to a safe spot and announce that you'll sit there silently until everyone's calm, says Mark Roberts, Ph.D., a clinical psychologist at Idaho State University in Pocatello. Then wait 10 to 15 seconds more -- the kids will hate that quiet time and most likely try to avoid it in the future.
Check in with your child.
Every so often, talk to her about riding with the other family. Don't grill her, but try to find out whether her seat belt is always fastened, for instance, and if the driver ever takes calls. If you're not happy about what you hear, discuss it with your carpool partner.