Our advice is to "choose wisely."
It is all too often the case that our Search Engine Optimization clients do not understand what keywords are going to result in buyers versus search terms for window shoppers. Are the keywords being used as "buyers" search terms? It is nice to get a lot of traffic, but it is better to get buyers, and of course it is best to have both ROI and search term traffic. The question is, how do we know if we are getting any of these? Are the search words also in your content so that you can satisfy the visitor?
You need a balance of search term traffic (what keyword phrases result in the most traffic), then making sure that those phrases relate to the content on your various pages, then making sure that you have a proper landing page that will hold the visitor, then making sure that those visitors actually buy or do what you want them to do. If you get one visitor per month for a search term, but one out of twelve spends a million dollars, keep that keyword! But if you get a million visitors and only one buys, and you lose money on that sale, then consider dropping that keyword phrase.
Of course, traffic is an unknown. Nobody really knows how many queries are performed for a keyword, and not all search words have the same click-through rates, so traffic is vague at best. But here is a nice little Bruce Clay, Inc. tool that may help:
Search Engine Optimization/KSP Tool
The information derived from our Search Engine Optimization/KSP Tool are daily approximations. In other words, they are daily averages derived from monthly averages. You should use the numbers as a proportionate traffic number since nobody really knows what an average day is, if there even is one.
We recommend that you also use the Wordtracker and the Keyword Discovery tools to refine your keyword list. We use these tools heavily in our day-to-day work, and find them sufficient to determine relative search engine keyword importance and form (use Wordtracker Multiple Search (Option 5) Compressed search to see singular versus plural search counts).
Next we need to know the click-through rates. While this may vary, the estimate is that PPC sites get about 2.2 percent on the average, and the free listings are triple that number. Using this information we see that certain keyword phrases can produce significant traffic. Of course, it is the job of the web site to hold that visitor once they visit.
So we need to make sure that the pages on the site have the search engine keywords you want to use. This is a lengthy process and can be accomplished several ways. We recommend that you use our visitor version of our SEOToolSet to evaluate your pages and keyword usage.