There are different types of SEO consultants and firms. Some are independent freelancers who will come up with an SEO strategy for your website and implement it for you.

There are also advertising agencies that usually engage in media advertising but have gotten on the SEO bandwagon. Because of their success with the media they may know time proven strategies to get your site noticed.

There are also interactive agencies that include you in the SEO process. Before you pick one you need to decide what your personal search engine optimization needs are.