more than half of business failures in this business isnt lack of customers its lack of the shop doing the right things to gain the customers
BBQ's and Bikini contests every weekend will bring in the customers //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
There are alot of good suggestions here posted earlier. Business plan, ALOT of research about what brands sell good around your area, etc. You should absolutely carry a few high-end brands you like, but ultimately a business is to make money...so don't be afraid to stock the shelves with Audiobahn, Pyramid, Pyle, and the liking, if that's what keeps the bills paid. Offer up your knowledge/ information to people who ask for it, but don't "push" products even though you know they may be better.
The radio station installs are a great idea, if you can trade that for some airtime. Also, get in with the local car clubs, hit the schools and universities and make friends with reputable people that can spread the word around about you. The high school kids and college students will likely be the majority of your business...so get to know what they like. And get some stickers/vinyl decals that you can give your customers to sport around, and get your name out there. The more people see a name, the more trusting they will feel about buying from you.
Alot of popular shops around here get customers in their store with other products like auto customizing (wings, wheels/tires, airdams, foglights, etc). I know it won't be easy just starting out to have a complete wheel/tire rack on display with plenty of stock, but let people know that stuff is avaible if they want it.
Good luck man..