What do you prefer for your web hosting business. And what is less expensive? Can you share your experience?

Personally, I find word of mouth to be the most effective.

Though I would vote on SEO first, because organic search results tend to be more effective, and if you know how to do it yourself, you're avoiding cost all together

I think you should combine SEO with SMO (social media optimization), it could give you some good result, however by any means SEO should be first.

SEO is cheaper, but both are essential to your online business.