Maybe you've past by a local Credit Union or heard from a friend about Credit Unions they use. If you are going to be financing a new or used car, then I would definitely join a Credit Union.
Financing through a Credit Union is always better than using a bank or dealership. For buying a used or new car Credit Unions are the only option I suggest. As my brother Aaron found when going to his Credit Union, the rate he was given was much better than any bank he went to. Also the rates for used cars are the same for new cars. At a a bank you might get quoted a new car loan at 5%, while used car loans are 10%. A Credit Union would charge you 5% for new or used cars.
Credit Unions have many advantages as well. They are actually non-profit and owned by the members not stockholders. They are typically small and customer oriented. Credit Unions offer great rates on other services and products. Typically your work will be affiliated with a Credit Union, so ask there first. You can look a Credit Union up in your area with the CUNA Credit Union Finder.