How to repair auto body rust?

From about.com:

If the rust spots are minor, find the rust spots and prep them for treatment. Remove the rust from the affected area by rubbing it with white spirits or rubbing alcohol and a sturdy wire brush or coarse sandpaper.

Scrape away any loose paint or rust. Then apply a rust-removing solvent to get the last remaining bits of rust from the area. Wipe clean with some rags.

Use coarse sandpaper to work your way down to a good paint sample on all sides of the affected area. Once you’ve reached unaffected paint on all sides, brush away the dust to clean the area.

Tape off the affected area to protect unaffected areas from the putty and paint you will be applying.

Apply glazing putty to the affected area as smoothly as possible. This will fill in all the pits or scratches so that the paint will evenly cover the area. Allow it to dry.

Get a sample of your car’s color either from a paint chip or an identification plate under the car’s hood. Take the sample to a paint or accessory shop and purchase the matching color, as well as primer.

Apply the primer and let dry. Then apply a fresh coat of paint. Do so smoothly, quickly and blend it as best you can with the existing paint on all sides.

After the paint is dry, polish and wax the affected area to finish.

If the rust has severely damaged the car’s body or frame, however, the affected areas may need to be replaced before the damage spreads.