Upholstery tacks and nails have two purposes: to attach padding or material to furniture and to add decorative accents. Most are made for indoor use, so they're not rust-resistant. If you need to clean them, all you have to do is gently rub them with a dry, soft cloth. Don't use polishing creams, as they could take off the finish. Upholstery tacks are sharp, so be sure to use safety precautions when working with them.
To upholster a dining room chair, take the seat off the frame of the chair and measure the seat from front to back and from side to side. Put a small mark at the center of the front of the chair and the middle of the back. Measure a piece of the material you're going to use to cover the chair, adding a few inches on each side. Mark the front of the material on the back side, and cut a small notch at the center of the front edge and the center of the back edge, so when you put the material on the chair it will sit perfectly in the middle. Remove the old material from the chair seat and position the seat of the chair on your new material, pulling the material to the back of the seat and lining up the notches on the front and back of the material with the marks on the front and back of the chair seat.
Using upholstery nails, hammer in a nail every inch (2.5 centimeters) along the front and back of the chair seat. Do the sides of the chair as well, and when you come to a corner, trim off excess material since you want the material to lie flat and not to bunch up. Reattach the seat to the chair, making sure that the front stays in the front.