My Guitar

I have a guitar and am trying to learn to play it. I received it from a great uncle that bought it about 27 years ago and never learned how to play it. I am trying to teach my self to play(using a book my mom found at a music store) and I don't know how well I am teaching myself. I can play a few songs (like "Yankee Doodle" and "Ode to joy" and other one string at a time songs). If any one out there knows and tips or anything, I would greatly appreciate them.
The guitar is a very cool instrument. I play the piano, the trumpet, and sing and the guitar may become my favorite out of all of them.
It is very cool.