#11 Clean the inside, too!
Vacuum and sponge your interior every time you wash your car. Dirt particles are abrasive, and spilled liquids, such as soda, can be corrosive. Vacuum your interior thoroughly with a powerful vacuum (small cordless models are generally too weak). Use the appropriate wand heads when vacuuming. The bare metal wand can mar and scratch surfaces. Sponge vinyl surfaces clean with a solution of mild detergent and water.