I grew up with a piano in the house. Like a lot of people, I tend strongly to feel like everyone ought to grow up about the way I grew up, and that distinctly includes having a piano in the house. A playable piano--all the notes sound, none of the keys stick in the depressed position, it's kept approximately in tune, and if possible it sounds pleasant. It should be easily possible to be walking through the house at a very young age, bored, and suddenly take a whim to sit down at the piano and plunk out some music on it.
The next step, if you can muster it, is to have people around who play the piano, to make sure the kids know what it's for. Every member of my family plays some piano; my dad his four or five rote pieces (Sentimental Journey, Turkey in the Straw, some godforsaken mazurka I can't name, and occasionally the chief riff from Flight of the Bumblebee), my mom a much larger repertoire (a lot of Chopin, some Mozart, Send In the Clowns, Cast Your Fate to the Wind, and a dozen others), things that blur in my mind into a loose category of music I grew up hearing. And Mom made sure each of the kids learned some, and we all kept doing music in this way and that as we grew up.
At the age of eight or nine, at least, I remember picking out compositions--fairly randomly--and memorizing them. I don't mean the things I played were just random series of notes; I would plink keys until I heard something that sounded nice, and then try some more until I found something that sounded okay when played right after the first thing, and so on. And I went on doing that; I haven't stopped in any definitive way. There was a big change, though, in the summer of 1988: I started playing with guitar as well. My dad has a lovely Martin classical he picked up for six hundred dollars in 1960. Martin isn't known for classical guitars particularly, but guitars are always individual; there are bad Martins out there, quiet Guilds, decent Yamahas, and at least one excellent Epiphone, to my knowledge. So as fate would have it, my dad's guitar--still one of the nicest classical guitars I have played, especially not counting guitars still inside stores--had the dual effect of making me a guitar snob for life and giving me a strong preference for classical guitar. (If you don't know the difference between classical and steel-string guitars, and you care, I'll tell you.)
My picking up the guitar, with any seriousness at all, took place on a specific day. I don't know the date, but one evening Dad showed me the fingerings of a few chords (half of which I immediately forgot) and some tips on proper position and technique (which I did not). After a bit he left me in the basement to work on it, and I stayed up til dawn and wrote a song. Not a great one, certainly. I was barely seventeen. But a song on the guitar, and with words--I have to this day never written any lyrics for a piano piece. I don't know what the difference was. Maybe I was just responding to the mass media, thinking of a guitar as a singer's instrument; I think it was a little more visceral than that, though. More likely the chief difference was that the guitar lends itself to learning chords first, and chords want a melody.
I've had more explicit instruction in the trombone than any other instrument, which is not to say all that much, in the end--certainly I'm no good at it and I haven't touched one since graduating high school. I have had some basic classes in guitar. But mostly it's been about the same trick as with piano--trial and error until I've got something that sounds good. The difference is mainly that with guitar I've done a lot more of it--and, importantly, that I've had feedback from other people.
I did tag-team songwriting for years with my good friend Andrew Dunn, which is a long story of its own. If Andy had a website, that would be cool, because I'd be able to link to it. But to the best of my knowledge he doesn't.
People want to know how good I am and it's a tough question to answer. My friend Brendan once introduced me to a friend on the subway as "an idiot-savant guitarist." That's at least the most economical description I ever heard. I don't have much of a grip on theory, certainly not the second-nature understanding it takes to improvise or transpose on the fly or any of those things that the pros can do. I don't read music so much as laboriously decode it, so I can't sight-read. Written music is useful to me only as something I might someday memorize. I have a good memory, at least. Also I have long fingers and a solid sense of pitch and rhythm and--thanks, Dad--good technique, as good as you generally find this side of classical players. My dad isn't a classical guitarist, by the way, but I guess somebody taught him right, back in the day. So no, I'm not good, or at least I'm not a good musician. But I'm almost certain I'm good at something to do with a guitar. I've been at it for long enough, at least.
I have been trying for two or three years now to screw up the courage (and the time, which is at least as difficult) to learn something about theory in earnest. On one hand I'm terrified of learning that everything I've ever done is derivative crap. On the other, I can't feel very good about hiding behind ignorance. And more than that, my most crippling deficit as a musician is that I'm utterly incapable of playing along with other people. I can only play by rote. It's a routinely embarrassing position to be in.
At the same time, I feel curiously disconnected from beginning guitarists who learn the basic chords and cobble them together without ever looking for chords in among those intersections of frets and strings.
One day I'll acquire the hardware, the software, and the know-how to make decent recordings and put them online. Til then I suppose you have to take my word for it.