11. Localization
Pick regional search engines you want to appear on based upon the countries you trade in. If you sell to France and you want to appear on Google.fr, the French version of Google, you should either host your site in France or have a French domain that your site can be indexed under.
It is important to continue repeating these steps on a structured basis and planning in advance of seasonal trends like Holiday Season. Over a period of time the keywords will change in relevancy as search terms evolve and the relevancy of your product range changes.
With an analytics system you should be able the see what words are working for you, the traffic they are bringing in and the level of conversion you are getting for them. With this information, you can see how much of an improvement you have made and also if any changes you have made have improved your results.