boulderguy -he nailed the subject, he definitely has a good understanding of marketing.
I have a great grasp on marketing so here are my 2 cents:
When running a business there are 2 sides INSIDE REALITY and OUTSIDE PERCEPTION. The inside reality is what makes you unique, what your business offers (3 experienced installers, 2 installation bays, free audio tuning, etc). The OUTSIDE reality is how the consumer sees you business. Your inside reality could be OUTSTANDING but you have to articulate and educate so that the consumer sees this too, otherwise you wonder how you're business is not growing even though you may have the 3 best installers in the state working for you for an example.
One of the main things you want to do is to lower the risk of customers. Offering free items helps you bridge the risk level most consumers have when dealing with new businesses. If you just offer a free system tuning they'll stop by (no risk)...then you can suggest some products you feel they would like. They might be apprehensive at first so using free services will get them in your door so they can find out how great your company is.
At one point you'll want to find your customer value hierarchy (what they value the most, 2nd, 3rd, etc. one thing is probably what I said before they are afraid that you won't be there in case they have a problem whereas they know Best Buy will be there even if your skills are better). When you have this your marketing will be better because you'll be able to fulfill the specific need they have.
Let's say the #1 fear of a customer is that you will not be there if their system has a problem after the sale and installation. Telling the customer "Were always available to you after the sale for support if you have any problems" will not cut it (anybody would say that so it is not believable), you have to get specific and articulate such as "If your system has any problem I'LL FIX IT + refund your installation fee + give you $20). Go bold with the marketing or don't go at all.
Here are some tips for marketing (a few ad ideas). There are many AD types but they all start with the headlines. I don't have time here to go into great detail but I'll explain a few and give a few examples you can use.
3 main headline types are: News, Inflammatory, How To.
News example: "Finally there is a professional Car Audio shop that has premium affordable, brands (list some), has staff that provides assistance in 2 minutes or less from when you enter the shop, and has prices at least %25 lower the Best Buy Circuit City and ABC Warehouse.
Inflammatory: "Crappy AMP $80, nice AMP that you like $90. If you like these prices stop by AccentSnow Shop."
"4 excuses stupid Car Audio buyers make to explain why their Big Box system sounds terrible" (and the body of the ad will list them). * It is harsh I know, like a hammer, but think of it this way to be successful you have to be like a hammer, make every strike count. Inflamatory ads are very successful because they shock people "Did they realy write that?" and get results.
How To example: "How to make your system sound better, without spending money on new amps, speakers or EQs" (then offer the free audio tuning of their system).
I have a lot more marketing advice. If you need something specific just ask me.
(1) Kenwood Excelon Head Unit KDC-X589 (24 bit Burr Brown DAC, 3 X 4 volt RCA).
(1) RF Punch 250A2 - running the components.
(1) Hifonics 6.5" Atlas Components (18db crossovers).