Shackleferd is pretty accurate on that one. When it comes down to it, the best way to learn of things you can do with the guitar is to read all you can. If you want to compose read all you can about the music theory, if you want to play well, read about technique. Read about the things that primarily interest you within the guitar and it certainly wouldn't be a bad idea to research reputable guitarists and find the ones that are masters of the techniques you like and basically learn from their expertise. Even if you don't like them, there's a lot of guitarists that we can all still learn from. Of course this doesn't necessarily mean you should completely change your tastes in music. Just that you really don't know what you can learn until you really observe someone else.