here's my $0.02

When I was quite young (15), I used to play with David Peel. We played in Washington Square Park a lot, and he would turn away from me because he was working the crowd. Since I knew Dave only knew six or seven chords, I soon learned how one chord led to another - known as resolutions.

There aren't an infinite number of these, and they all make sense once you understand them.

Two years later, I started doing "club dates" (here in NY, that's what we call weddings, bar/bat mitzvahs, coming out parties, quadrilles, etc.) I'd be thrown in the lion's cage with guys who played with the big bands of the 30's and 40's, expected to play any song from any period, with no sheet music. Often without even given a key. That's when it REALLY clicked in.

Sure, I screwed up - a lot. Came home from gigs embarrassed and disgusted. But I figured out which resolutions I had trouble with and got to recognize them. I still get caught out sometimes, especially now that I'm old and lazy(er), but the fact is some chords lead to a few possible other chords. By learning songs such as "On The Street Where You Live", "Cherokee", "Stella By Starlight", "Have You Met Miss Jones", and really analyzing how they go from one chord to another, you'll get it.

You'll be able to play anything, pretty much on the spot, within the first chorus or two. As long as you know how the song goes. You might also listen to anything by that lunatic Burt Bacharach (I mean that in the most respectful way) and Steely Dan (Aja album) once you get the hang of it, just to test yourself. Paul Simon's "Still Crazy After All These Years" is a great model of using every damn note you can in the melody and choosing chords accordingly.