Business cards are great to give someone a way to contact you, fast - just grab it from your pocket and lend it. But it'll not market you anyhow.
Like already said, best thing is word of mouth - people telling other people something NEW, different, detailed, respectful, etc is happening at your place.
However, you're better covered if you have something to show potential customers, like a site, portfolio, or even threads in a forum like this may work. You can say you've worked on a lot of exciting cars, but I'm sorry to tell you - it's worthless without pics.
Document your work and find a place to share it. Whenever I receive a call, I forward an e-mail to customer before he / she comes for evaluation.
(Sorry if it makes answer long, I'm trying to share ideas so you can adapt to your way of doing it)
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The e-mail is something like this:
Preto / Black
Mercedes 2012 C180 Preto - Detalhamento, Correção de pintura e Vitrificação.
http://www.autogeekonline.net/forum...80-3-steps-pinnacle-black-label-coatings.html
2014 BMW 320i Preto detalhamento e vitrificação
http://www.autogeekonline.net/forum...w-320i-full-pinnacle-black-label-coating.html
Kia Sportage 2013 Preto vitrificação
http://www.autogeekonline.net/forum...ge-black-correction-black-label-coatings.html
2014 GM Tracker Preto detalhamento e vitrificação
http://www.autogeekonline.net/forum...acker-new-car-detail-black-label-coating.html
Prata / Silver
Mercedes C280 detalhamento e vitrificação
http://www.autogeekonline.net/forum...280-detailed-coated-pinnacle-black-label.html
Corolla 2012 detalhamento e vitrificação
http://www.autogeekonline.net/forum...ll-detailed-pinnacle-black-label-coating.html
Civic 2013 Prata detalhamento e vitrificação
http://www.autogeekonline.net/forum...c-full-detail-pbl-coating-coating-booster.htm
PT Cruiser Prata reparos, retoques, detalhamento e vitrificação
http://www.autogeekonline.net/forum...uiser-fully-detailed-black-label-coating.html
Branco / White
2013 Pajero TR4 Branco detalhamento e vitrificação
http://www.autogeekonline.net/forum...ull-detail-pinnacle-black-label-coatings.html
2011 Citroen Aircross - Correção de Pintura, Detalhamento e Vitrificação
http://www.autogeekonline.net/forum...-correction-coating-pinnacle-black-label.html
Azul e outros / Blue and Others
2013 ford Ranger Azul vitrificação
http://www.autogeekonline.net/forum...e-full-detail-2-step-polish-pbl-coatings.html
Audi A1 Dual-Tone Azul/Prata Detalhamento, Correção e Vitrificação.
http://www.autogeekonline.net/forum...correction-detailing-black-label-coating.html
GM Zafira 2011 Full Detail + Vitrificação
http://www.autogeekonline.net/forum...e-makeover-pinnacle-black-label-coatings.html
Fox 2013 Descontaminação, Polimento e Vitrificação
http://www.autogeekonline.net/forum...ion-detailed-coated-pinnacle-black-label.html
Gol 2013 Preto correção de pintura e vitrificação
http://www.autogeekonline.net/forum...most-popular-car-brazil-corrected-coated.html
Corsa - remoção de resíduos de cola
http://www.autogeekonline.net/forum...ck-corsa-popular-car-removing-super-glue.html
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They can look at cars by color, or any other they have curiosity.
Sharing my work here is beneficial to what I do. I'm better showing my work to whoever knows better or really enjoy the craft. You must be 'brave' to show the greatest a little of what you're achieving, thanks to them.
Another good thing is to always get suggestions and new ideas to improve the work you're doing.
Also, they can access AG store and knowing what I use (products and techniques always shared) understand why my quote is higher than the guy next corner.
It's said to avoid being cheap (TRUE!), but remember you must start somewhere. Getting good cars from known people are a good way to start building your portfolio.
Hope that helps,
Kind Regards.