As "Popular Mechanics" observes in the article "How to Repair Your Car Scratch: Saturday Mechanic" (www.popularmechanics.com), not all scratches are created equal. Upon close examination it may be discovered that some marks are only sitting on top of the paint surface and don't actually qualify as scratches. But if the clearcoat or any of the paint layers of your car have been damaged, you do, unfortunately, have a scratch that needs your attention.
Determine the Damage
Draw your fingernail over the surface of the mark at a 90 degree angle, and you will be able to feel if there is a gouge or scratch or if the mark is simply a smudge. Marks that sit on top of the paint can often be removed by rubbing them with a soft cloth and adhesive remover. If this is not enough to remove the damage, wash and dry the affected area, and then try buffing the spot in a circular motion with rubbing compound. When the mark disappears, use a clean cloth to remove all the rubbing compound and clean with polish. Seal the area with a quality car wax.
If you have a scratch, wash and thoroughly dry the affected area. For very light scratches, buff the damaged area with a rubbing compound and then polish with a polishing brush and polishing compound. If this is enough to make the scratch disappear, follow up by buffing with a clean, soft cloth and applying a light layer of car wax to seal.
If this is not enough, consider taking your car to an auto bodyworks garage or sanding down the scratch yourself. By sanding, you won't actually be "repairing" the scratch but will be sanding down the surface immediately surrounding the scratch to make the surface even. Apply shoe polish in a colour contrasting with your auto paint to the scratched area. The polish will become stuck in the scratches, and this will help you identify where repair is needed while assuring you don't over-sand. If you are not experienced in sanding metal, consult an auto body expert. The key is to sand slowly and lightly, moving up and down the length of the scratch until you see the contrasting mark disappear. Polish the sanded area with rubbing compound and follow with polish applied with a polishing wheel. Lastly, give the area a light hand buff with a clean cloth and apply car wax to seal.