What makes an SEO to?

Here are a few keywords:

Meta Tags

robots.txt

XML Sitemap

Keyword Analysis

Keyword Optimization

No-follow links

Redirection (Forwarding)

Canonicalization (source reference)

A few notes about this: Meta tags and search engines read except some crazy webmasters nobody. The robots.txt file tells the search engines what data and what they cannot crawl. Without giving it index everything they find. XML Sitemap can affect the speed at which new pages are indexed. But an effect on the ranking they have not to my knowledge. Keyword analysis means that one finds the most 'rewarding' terms, which have the most search volume. In keyword optimization the content is modified accordingly. In the worst case is called keyword stuffing. The text is then loaded with the concept and the basic unreadable. Typical case of a search engine optimization, the SEO has forgotten that even SEO will lead to more visitors. No-follow links indicate whether the search engine is to follow the link or not. This is for any normal person completely irrelevant. The redirection of pages whose URL has been modified, is reasonable in the long run but also get the Google Redirect without regulated.

In short, all these SEO measures are irrelevant for the human user of a page. And I would claim that they have a minimal impact on the ranking. Therefore hiring an SEO is not worthwhile in most cases.