SEOBook recently offered a straightforward overview as to what expect when you're looking to buy search engine optimization (SEO) services.
For the record, I see SEO as a long term process rather than a one hit deal.
For the best results SEO takes time, often six months or more, and typically involves restructuring websites and developing content as well as generating links.
I also put a lot of focus on what happens post click ie. once a visitor arrives at your website how can I most effectively convert that visitor into a sale or lead.