http://guitar.about.com/library/blguitarlessonarchive.htm
http://www.guitarforbeginners.com/
http://www.guitarnoise.com/
I started teaching guitar at age 19, too. I’ll give you my approach and some things that I’ve done to help my students.
I just went out and bought a guitar one day (age 14) and started tinkering around. I tried to learn some songs by ear and copied some stuff from friends who’d been playing awhile. Well, that wasn’t working out that well, so I decided to start learning exactly how the guitar “worked”, meaning I started studying music theory in high school and on my own through books.
At that point, I realized I was taking a far too academic approach to the instrument and my “playing” sessions all became practice sessions. Practice is extremely important, but to quote the old phrase “all work and no play makes Jack a dull boy”, and it did. I was a machine after some time, practicing eight to ten hours every single day. Obviously my technique and fingerboard knowledge improved exponentially, but I sucked. I had all of the physical skills, the virtuosity, but I wasn’t capable of playing from the heart, being passionate and creating my own music.
I narrowed it down to this approach after many long years.Learn how the instrument works, learn the fretboard and the location of all the notes, practice every day and make that “practice time” really strict. I used to use a digital clock and a metronome (please don’t forget the metronome) and played every scale that I knew in every position for three minutes straight, increasing the tempo on the metronome every one minute to push myself harder.
Separate your practice and your playing time. Practice first so that you’re plenty limber, then just play, play along with CDs and even improvise of songs that you like. Be sure to experiment a lot during your playing sessions. That’s where you’ll really start to grow as you on the instrument, not as a copy of someone you admire.
On that note, try to learn from players that you do admire. Learning their music and techniques and expounding upon them will help you create the style that you’ll ultimately be happy with, an amalgamation of your favorite plays made into something of your own.