What should you do if your car starts to skid?

First, stay calm and don't panic. The key principle is to steer in the direction you want the front of the car to go. This is often called "steering into the skid." Here's the step-by-step for the most common type, a rear-wheel skid (fishtailing):

1. Ease Off the Accelerator/Brakes: Immediately take your foot off both the gas and brake pedals. Do not slam the brakes—this will lock the wheels and make you skid more.
2. Look & Steer: Look where you want the car to go (your intended path, not at what you're sliding towards). Then, steer smoothly in that direction. If the rear is sliding left, steer left. If it's sliding right, steer right. You're trying to align the front wheels with the direction of the skid to regain traction.
3. Gently Correct: As the car straightens out, you may need to steer back the other way to prevent over-correcting into a skid the opposite way. Do this smoothly.
4. Once Recovered: When you feel traction return, you can gently apply the accelerator or brake as needed.

For a front-wheel skid (understeer), where the car plows straight in a turn, ease off the gas and very gently reduce steering input until the front tires regain grip, then steer again.

Practice in a safe, empty parking lot in the rain or snow if you can. The goal is to make the reactions instinctive.

A great visual guide: Defensive Driving - How to Correct a Skid