I am a self taught musician, and primarily a guitarist, and wanted to share some truths I've discovered in my journey. While some of the things I talk about seem to be extremely obvious, they weren't obvious for me when I picked up the guitar and decided to learn to express myself with the instrument. (As a side note, that is a goal I haven't accomplished yet expressing myself with the guitar though I am a lot closer than the day I started). Following are some observations:
1. Learn cover songs, not for their own sake but for the peripheral things this teaches you. Learning cover songs does a lot of desirable things. For one, it trains your brain to memorize a song. It causes you to stretch your technique and ability to play the more complicated passages and it gives you examples of music theory in practice. The trick is to always pick songs to cover that force you to stretch your ability, and that you will enjoy playing. A friend of mine once told me when I was starting out that learning to play cover songs is not being a musician; it is being a CD player. I can see that this would be the case if you are just blindly reproducing songs that aren't challenging your skills, but if you are learning songs that are a stretch for you, and you are paying attention to the chord progressions, etc., then it will always be a worthwhile learning experience.
2. There is nothing wrong with trying to play like your favorite guitarists. I seriously have watched hundreds of hours of concert footage of my favorite musicians, and I do try to emulate them. When I apply vibrato or just a string bend I am always either trying to emulate Carlos Santana or Steve Vai. When I am playing a complex melody I am trying to emulate Frank Zappa or Robert Fripp. When I am trying to play some really solid rhythm work then I am trying to emulate Adrian Belew or Dave Mustaine. When I compose, depending on the type of music I am working on, I am trying to emulate Dave Mustaine, Frank Zappa or Isaac Brock. When I write lyrics and vocal melody I am trying to emulate Isaac Brock, Frank Zappa or Jeff Mangum. I think the trick is to appreciate your guitar heroes for their strengths and to attempt to emulate their strengths instead of just copying their riffs and licks.
3. Don't practice scales and modes for any longer than is absolutely necessary. We all have different goals as musicians, and maybe your goal is to be a pure shred lead guitarist. If this is the case, then you may need to spend hours a day practicing scales, modes, etc. But my primary goal as a guitarist is to make music that I enjoy, and while I do enjoy improvising solos and fast single note runs, it is not my end-all be-all goal. I've found that when I practice scales and modes for too long that I tend to enjoy playing guitar less, and I'm more likely to find excuses to skip my practice time or cut it short. However, when I practice scales and modes as my warm up for no longer than 5 10 minutes, then I notice my fingers are limber, I retain more from a memorization standpoint and I enjoy the rest of my practice much more, and so I tend to practice more often and for longer.
4. Don't learn any more music theory than is absolutely necessary. Learning music theory is great and very useful, but trying to take it all in as quickly as possible is a bad idea in my mind. I would say at most learning the major and minor scale and the pentatonic major and minor, and then learning basic chord theory is plenty of music theory to start out with. I know people who have studied music theory to the point where they lose interest in playing and have told me they have lost all joy in playing guitar because the whole time they are playing or writing they are more intellectually absorbed in music theory instead of the SOUNDS they are playing or composing. Here is the thing about music theory it is theory it is a bunch of good ideas that people have had in the past that have become a curriculum for anyone wanting to learn guitar or any other instrument. And music theory should be a tool you use instead of rules you have to follow, and if you find yourself intellectualizing the creative process to the point where you aren't enjoying your instrument, then it isn't serving its purpose.
5. Learn the CAGED system. This is probably the most valuable learning system I've discovered. The premise behind it is training your brain and muscle memory as to where all the notes on the neck are, and learning the basic chord shapes that can be applied anywhere on the neck, learning some very basic chord theory and using this in order to create any chord variation you need in any position very quickly and teaches strategy for better soloing. I'm not doing a very good job of explaining the CAGED system, but there are some awesome DVDs called Fretboard Navigator that are worth checking out.
6. Play with other musicians as soon as and as often as possible. It doesn't matter if you aren't that good yet, it doesn't matter if they don't play the type of music you like, it doesn't matter if you don't have the best equipment, etc. When you start playing with other musicians you begin to establish an internalized sense of meter/timing that you will not get from a metronome. When you play with other musicians you will learn things from playing with and watching them even when you think they have nothing to teach you. When you play with other musicians you are going to meet other people with similar instruments that will help keep you motivated to learn and play. Also, playing with other musicians is a lot of fun and very fulfilling, even if they aren't playing the music you would be playing on your own.
Well, that is all I have to share right now. This is the first column I've ever written, and I hope it is helpful.