I don't know that song, but the good old G blues scale is always handy.
Go here: http://www.looknohands.com/chordhouse/g ... ex_rb.html
On the tuning pulldown menu, select "Open G." DGDGBD
On the pulldown menu for "Scales" you'll see two handy options: In the "Regular Scales" you'll see "Pentatonic Blues Scale." That's actually the minor pentatonic. Under "Exotic Scales," you'll see "Blues Scale." That'd be my pick. It's got an additional b5 note that you don't want to hang on, but it's great in passing. (They call it a #4 instead of a b5, whatever.) It'll give you a dandy fretboard map of your scale.