A few more things you may want to consider are the look of the guitar, the pickups, if it is a hollow or solid body, the price, and the reputation of ...
This Instructable will be a guide to what you should look for when buying a guitar. I will address all of the different aspects that you should consider so that you can know what kind of guitar will fit you best. It will be directed towards buying an electric guitar so if you are looking for an acoustic this Instructable isn't for you. Also, I know this Instuctable doesn't cover every aspect of guitar shopping but it covers some of the more important parts.
Step 1: A Good Fit for Your Style Of Music
One very important thing that you should consider when choosing a guitar, is the type of music you will be playing. For example, if you play a lot of hard rock or heavy metal, you might want to get a guitar from Jackson, B.C. Rich, ESP or Ibanez. These brands make most of their guitars with thinner necks and lower action (strings lower to the guitar neck). Both of these features allow for faster and easier playing so these are good guitars to shred on. Another example is if you play a lot of blues you might want a Fender Telecaster or a Gibson Les Paul. These guitars are mad with smoother sounding pickup which are perfect for soft rock, blues and jazz. It is also very important the the guitar you choose has the right sort of sound for your preferred genre.