First, have you created a Webmaster Tools Account, a Google Analytics Account and a Google AdWords account? If not, do that, start there because they have a tool that will tell us exactly what people are looking for using the google search.
Once these are created you are going to start collecting valuable information about the visitors to your site.
In Webmaster Tools we can see the following basic information on the Dashboard:
The next image indicates this site is coming up in searched but that this site could perform better for “clickability”… this could be a simple tweak with page descriptions and metatitles.