MoreVisibility's Joe Laratro breaks search terms into three categories for online retailers--general keywords, shopping keywords and buying keywords, and instructs Webmasters to help them optimize accordingly.
General keywords like "televisions," for example, can be tremendous traffic drivers, but "due to the range of intention among shoppers searching these terms, much of the traffic they generate may be untargeted or irrelevant," Laratro says. They can also be difficult to snag high rankings for at a low cost.
Meanwhile, shopping keywords like "plasma TVs" signal that searchers are further along the purchase pathway, and are good sources of more qualified traffic. Buying keywords are much more specific, like "50 inch plasma TV in Denver," but Laratro says that the most successful sites are the ones that find an effective mix of all three.