There's a very interesting thing about doing SEO and that's the fact that you have to be a puzzle master. You've got one piece of information here and another piece of information over there and somehow, you're supposed to string it together to be something functional. So you do keyword research but that's just the tip of the iceberg because after that comes all of the long-tail search terms that are impossible to predict ahead of time. Well, you can to some degree using resources like yahoo answers and stuff but for the most part you can't. That's where tools like stat counter and google analytics and also your cpanel stats come in. These resources are basically discovering keywords for you. But on the downside, they don't tell you where you rank in Google. That's the part about being the puzzle master.

Now if you got in on the Link Liberation thing or maybe you didn't, Dan and Leslie have an interesting concept called zone-based SEO, which you can watch here:
There’s NO Excuse for Having a “Small” Business on the Internet (Part 2)

In short, you basically work only keywords that are on the first page of the SERPS and ignore all the others. While I think this is efficient, there are other low hanging fruit search terms that are also worthwhile and yet they may not be on the first page. You see, in your analytics or stat counter or cpanel stats, any keywords that are bring you traffic and yet, you're not on page one for those keywords are keywords that a. are likely that you'll be able to move up easily for them and b. have a high amount of traffic once you get better rankings. Of course, you won't know this unless, you're rank checking the keywords in your stats. So the short story is rank check your stats and work those keywords bringing you traffic.

Happy Hunting,
Chris