Outside

• 1). Wipe down your windows and windshields with a mixture of vinegar and water the previous evening. Use three parts vinegar to one part water.
  
  
• 2). Cut out sections of plastic dropcloth that fit over your windshields. Kevin Davis writes on NJ.com that he was able to prevent frost buildup on his front and rear windshields this way.
  
  
• 3). Apply a chemical anti-icer to the windows if the other methods fail.
  
  

Inside

• 1). Inspect the weather stripping around all the windows and windshield. Replace any that you find loose.
  
  
• 2). Inspect the windshields and windows themselves if you've had them replaced. They may have been installed incorrectly, leaving an avenue for moisture to get inside the car.
  
  
• 3). Check inside the trunk of the car. If the trunk interior is wet or feels humid, there may be a problem with the weather stripping within the trunk. According to Car Talk, this moisture can work its way into the car and result in a frosty interior.