Wana learn Rock Guitar. Prerequisits?

If you've been playing piano for 15 years then you might have developed a good ear by now.. Learn how to play the basic chords on guitar... C, D, E, G, A, D7 and throw an F in there... You'll be amazed at how easy all the songs you hear on the radio are to play. Just listen closely for the base/bass (i.e. top thick notes on the guitar..and try to reproduce what you hear by playing only those notes (to start)... then place your fingers down around the notes you're hearing to create the full chords around what you're hearing... and see what happens. I play guitar and was classically trained also... this is how I figure most of the stuff I hear. Now, you might run into problems trying to do with Dave Matthews, John Mayer songs, etc.. because they're freestyling and doing variants of the basics. Just keep it fun, let the creative juices flow and enjoy every note.. I'm of the philosophy that one note leads to the next and it takes a good ear to put it together.

In order to go from classical music to rock you need to quit school and take lots of drugs. Rock music stems from medieval music and you're brain is too developed to be able to play it properly.