So now we know people are finding your site for the search terms that you've targeted. We're done right? Well not quite... What we've covered up until now will help you analyze what's going on with your top search terms. But many sites get at least hundreds of different unique search terms in a month. Most of them are not targeted terms and are probably not drawing in very much traffic, so they're worthless right? Quite the oposite.
The bottom half of your top search terms often hold some of this gold we're panning for when we look through log files. They will often be more complex terms. Where one of your top targeted terms may be show dogs, one of your bottom terms might be buying quality combs for show dogs. You're clearly not going to get much more traffic than you already are by targeting a specific complex term like buying quality combs for show dogs but it tells you that someone out there is looking for combs for dog shows. So what page did they find when they searched for this (check your raw logs for this info). In most cases, they'll have found something off topic such as a page where you talk about the need to comb a show dog before buying it.
Let's analyze this for a second. We've determined what someone was looking for when they found something that sort of fit. Imagine the business a grocery store could do if it could know what a customer was really looking for when they were looking for something and couldn't find it. You can go step further and look at what other pages this person may have visited on your site after they performed their search for buying quality combs for show dogs. Anything else of interest there?
I will admit that we're getting a little fine grained here and you won't necessarily be able to do this kind of fine grained log analysis when your site is hugely successful and has more traffic than you know what to do with, but in the meantime this is something very real that you can look at to help your web site cater to the people who are out there visiting it.