Most people find a dealer by looking up "Garage Doors & Door Operating Devices" in the Yellow Pages. Though some of the companies listed in your directory might manufacture their own doors--particularly wood doors--most buy garage door sections from large manufacturers. Some local dealers sell only one manufacturer's doors; others sell a variety of makes. It pays to do your homework before talking with dealers by contacting major manufacturers (see the resource guide BELOW), requesting brochures and product information so that you can compare features. Then contact dealers in your area.
Though some garage door companies have showrooms, most will send a salesperson to your home to discuss your needs, show you manufacturer's brochures from the lines they carry, measure your old door, and get your signature on the dotted line.
Some home centers sell a few makes of garage doors that do-it-yourselfers can install. If you buy a door to install yourself, be sure it comes with complete, easy-to-follow instructions. Also be sure the door includes an extension spring containment kit--without it, extension springs can be very dangerous.