I am a SEO (Search Engine Optimization) enthusiast who happens to practice their trade in-house. My introduction into SEO happen several years back during an engagement by my current employer with an outside SEO agency . This was back in the early days of SEO when life was much simpler. Not everyone was drinking the SEO Kool-aid, thus some simple optimizations took you a long ways. This was also in the day when a true measure of success was your SERP ( Search Engine Rank Position).
The best part of an agency engagement is sucking the knowledge out of their brains. A typical agency produces enough documents to keep any person seeking SEO knowledge quite happy . What I have found is that these documents no matter how old they are contain the fundamentals of SEO that do not change much over time. Any organization that is serious about SEO and does not have an in-house resident expert should engage an agency but at the same time have someone in-house ready and willing to reap the rewards of all this expert knowledge.
What skills should the future in-house expert possess to make the most out of the "sucking process"? SEO requires a diverse set of skill sets that is hard for any single person to possess all of them. Experience in the operations of the website is quite beneficial. This includes architecture, the content management system and all the technologies that go along with the makings of a website. Also important is copy writing and authoring of content for your site. If you are in marketing, this is a bonus. If you are in management you will be able to reinforce the importance of a good SEO strategy. Maybe this is not a skill but I would rate having lots of friends in all the right places to be quite an asset. There are many individuals who you must interface with during a successful SEO campaign and knowing who they are is half the battle.
Ok back to skill sets that are handy for someone contemplating becoming an SEO in-house expert. Experience with web analytics is a must. Almost every website has a web analytics package these days. At the very minimum having access to the tool with the knowledge to find out where the search engine data is will enable you to undertand your current state and what impact your SEO campaign is having. If you do not currently possess this skill then you better add a web analyst to your list of people to know!
Once you work through an entire SEO campaign with an agency you will get a good feel for all the types of skill sets required for success. Small operations may only have one person while large sites may have a couple dozen individuals contributing to the success of SEO. Grow the team over time, start out small and keeping adding important skill sets as your team matures. It will all be worth it in the long run.