I still have a LOT to learn, but here has what has helped me a lot so far:
1) Lessons from a good teacher in person.
2) Instructional DVDs such as Brent Mason's, Terry Downs', Redd Volkaert's, Doug Seven's, and Ken Carlson's.
3) Transcriptions/Tablature of songs I wanted to learn.
4) Playing live, jamming with friends, being in a band, playing on stage. Your learning gets accelerated once you perform in front of people.
5) Learning songs on my own by ear. The Tabs & Lessons are great "foundation builders" and I still use them to this day, especially for stuff more advanced than my current level, but learning by ear is great for development.
6) Writing Songs. Even the most elementary chord changes help one appreciate the craft of songwriting.