Keyword research is the key to being successful with your website but there are a couple of things you need to keep in mind.
First off, you want to be sure that you go for keywords that get enough searches!
I made the mistake for quite some time when I was researching keywords of targetting those that didn't really have a lot of searches (I made a key error when using the google keyword tool!). Then I wondered why the keywords didn't bring in the traffic I thought...