These tutorials do not necessarily represent everything there is to know, so check with other sources as well.
- Be careful about accepting SEO offers via telephone or e-mail. (Because of: Scams and clueless clowns.)
- Always consult official sources. (I.e. Google, Yahoo, Bing, and so on.)
A good web- developer / designer should be able to handle SEO from the start, so you will not have to hire third parties later.