My learning process has been all over the map. I started out learning from Mel Bay (and the like) books, and got some pointers from a guitar instructor that was dating my sister for a time. As resources started becoming available on the internet, I started leveraging that, but as was mentioned, sometimes you get something that sounds like the song as opposed to the real deal, which often sounds a lot better. I found that disappointing in particular when I discovered that there was a right way to play Neil Young's "Tell Me Why", contrary to what I picked up and practiced for many hours on someone's best interpretation. Best to make sure you're getting the real deal for songs that you really care about. Sometimes you can find video of the artist performing the song to verify the accuracy of what you find on the net.
DVD instructions are another great resource. In particular the Stefan Grossman instructional videos are fabulous for fingerstyle guitar and the blues idiom. He also provides a wealth of information to supplement the instruction, including discussion about the original artist and their technique, music theory, and historical origins of music. The fretboard and picking hand shots are easy to learn from. Can't recommend his videos enough.
I think working with an instructor is something that should at least be explored. I spent about a year with an instructor, and it wasn't ideal, but I did pick up a good bit of theory from him, that I don't believe I would have gotten around to on my own. For example, discussions about tonal centers, chord families and progressions, and how 7th and minor chords are used in music. He would point out the compositional excellence in certain songs that made the music theory points he was teaching me. Having said that, there are good teachers and bad teachers. You have to let them know what you want to do, and be willing to follow and work with their approach to learning.
I also recommend the book "Fretboard Logic" for learning the CAGED System as a means for breaking out of the open chords and understanding chords and scales over the entire neck of the guitar.
Playing along with music, and using a metronome are good ways to establish timing. So is playing along with others, which is the one area I have never taken advantage of. Guitar seminars and camps are also good learning experiences, although I think this method is best suited to more advanced players.
