[Stratrat]

With all the tab available nowadays, you can start copping other peoples' solos pretty quickly. You won't have the faintest idea what you're doing or why you're doing it, but once you learn them and work your speed up, you'll be able to play them.

To really solo (i.e., be able to improvise on your own without playing somebody else's solos, or to understand other peoples' solos you're playing), you need to learn the fretboard and a decent amount of music theory, to understand what notes will sound good over what.

From there, you can use scales/modes, or you can use chord tones. Scales are a "safe" approach and are probably the easiest way, but they can be somewhat limiting. You can use the A minor pentatonic/blues scale throughout a song in the key of A, for example, but you're only giving yourself a handful of notes to choose from. Chord tones allow you to diversify the sound more, and also blend more sweetly with the melody of the song. To quote Kirk, "melody loves chord tones".

My story - I played rhythm guitar in a backyard band when I was a teenager. I could play open and barre chords, but knew absolutely nothing about music theory and couldn't solo to save my life. At best I could cop a few licks from other peoples' solos, but had absolutely no idea what I was doing - I was just parroting the notes I had figured out from listening to a record over and over again. I had no idea what notes they were, how they related to each other, whether they were scale notes or chord tones, etc....all I knew was to place 'this' finger at 'that' fret, followed by 'this' finger at 'that' fret, etc. Beyond that, I was completely lost. Several of us would get together often for jam sessions, and we would often set up a simple chord progression (the middle of "Free Bird", for example), and guys would take turns soloing over it while the others played rhythm. Every time I tried improvising my own solo over it, it was nothing but a bunch of weak, discordant notes that sounded terrible and I would quickly switch back to playing rhythm while everybody else wailed away at solos. I had no idea what a "minor pentatonic scale" was, nor any other kind of scale. My total lack of knowledge severely crippled my playing, and since I was self-taught and couldn't afford lessons, I had no idea what to do to improve. I learned how to do string bends, how to do the Eddie Van Halen tapping stuff, etc., but could never find the "right notes" that sounded good because I didn't know what I was looking for or where to find it.

When I started playing again a couple of years ago, I decided that I was going to really learn the guitar this time....learn all the things I had been ignorant of when I was a kid, and see if I could make a little nicer noise than I did back then. I'm still definitely no whiz at it (I'm somewhere past "beginner" but nowhere near "beyond"!), but at least now I know what I have to learn/do and am working on it. I learned the minor pentatonic/blues scales and the major scale and fiddled with them, then bought Kirk's "Plane Talk" and learned more about music theory and the guitar from that book/CD than I had ever known in my life. I'm still working on assimilating all that knowledge in my head and transferring it to my fingers, but it certainly opened a lot of doors for me.