Killer simple as far as I can tell, but I probably couldn't have figured it out a year or so ago when I was firmly in "beginner with no ears stage," so I thought I'd share. It's in 4/4, and the chords are C, Am, F, and G. During the verses, it's consistently one full four-beat measure of C, then one of Am, then two beats F, two beats G, and two beats C again before starting over into the next verse. The picking pattern is a great one to start with for folks who're having a hard time (azchords.com)