
I'm mad because the same question was posted in a thread last week, but when I went to get the link to post here, the thread had disappeared, along with all our ideas we posted to help the guy. I suspect he deleted the thread, taking our ideas with him so no one else could benefit from them. Nice.
Anyway, I'm going to try and nutshell what I posted there.
I'm not a detailer, nor do I have a marketing or advertising background, so user beware. Oh, and if you successfully use either of these ideas, let us know, and send me money (5% of first year's increase in business ought to do it

).
Anyway, the first idea that sprang to mind was to come to an arrangement with a store that sells detailing products you use. On a sunny Saturday, you set up in the store's parking lot (visible from the street would be bonus), with a beautiful car in dire need of attention, and then you detail half of it, taking your time, using products the store sells. Jazz it up a little with those fluttering strings of pennants you see at car lots. You have someone on hand to book appointments, and you patiently answer questions, no matter how dumb (I think a good "car-side" manner is a must here). It would be great if you had a canopy with your logo etc on it; you'd certainly want prominent signs saying who you are etc.
Maybe you could even sell hotdogs and refreshments, and make some dough out of the deal.

Another way to make dough that day would be to take a cut of the products sold that day above usual volumes. I wouldn't try that one on with the store until you've secured the parking lot arrangement, though, and don't hold your breath for a favourable response.

If it really worked out for the store, you'd have better future bargaining power.
If it's a chain store, maybe you could tour (though you might run out of beautiful cars in bad shape -- maybe you could offer a free detail to customers who let you do the demo on their cars). If it's a car you can keep your hands on for a while, you could park it in prominent places, still half detailed, with brochures/business cards available at the car. Maybe you could get one or two magnetic signs that stick on cars, saying "Car Detailed by Donny Doowop, Detailer to the stars. By appointment only. Usually a week's notice is required, so phone early etc. "
Another idea is a more standard approach. You advertise and then give detailing seminars. Of those who attend, some will learn and do themselves (the nerve!:angry ), others will think you need to do it for them. Whatever you do, don't tell them about Autopia!

Even many of those who don't go to the seminars will come to believe that you're the local expert, if they see your ad enough times in the paper.
Good luck,
~3W