I'm a software developer. (Just not that great at creating graphics.)
I'm not a pro at detailing but getting stuff to do on the side so thought I'd tinker with Microsoft's Silverlight some and build a small company website.
I started a site the other week but haven't had time to work on it since.
Home
(You'll need to install Silverlight 3 to see it.)
Nothing major to it yet but have the menu laid out with the topics. You will probably want to list your services.
Maybe a FAQ page explaining what you do, why and the differences that separate you feel separate you from others in your area.
Show pix of your work. I've posted some stuff I did on a local website and already had two people asking me to do their cars.
Testimonials as has been mentioned are good. Make sure you have a contact us page.
If you are looking for a place to host, I've started using godaddy as they have some good prices and admin tools for managing your website.
Finally, I really feel how to sites with demo's and detailed explanation of how to do things helps. The people will appreciate and I think see you do it because it's a passion and not just in it for the money and appreciate you sharing with them. Face the do it yourselfer's will find info anyway but if you help them enough, they'll be something they are afraid to tackle and come to you.
The others looking for some where will to go will be able to see you know what you're talking about and earn a respect for you and your passion.
my 2 cents.
If you aren't a developer, there are some templates out there that are pretty cool. Some I found by searching on "Car Wash" but should be easily customized to do what you want.
Good luck.
