To prevent vehicle rusting, regularly check for chips and nicks in the car's paint, and wash the car's undercarriage periodically. If the carpet is exposed to salty water during the winter, remove it using rug shampoo.
If you find any chips in your car's paint when examining it, first wash the area with a rag dampened with mineral spirits, then let it dry. Afterward, use a touch-up brush to fill in the gap with paint. If there is already rust in the nick, use sandpaper of 220 grade or higher to sand it down to the bare metal before painting over it.
To wash your car's undercarriage, either use the hose at a manual car wash, or simply place a water sprinkler on full blast underneath the car. The grime built up in the wheel wells and undercarriage can trap moisture and lead to rusting, so it is important to clean the area regularly.