Well, I play an obscure tune by B. W. Stevenson (He wrote "My Maria" made famous by 3 Dog Night). It's called On My Own. It has a ascending couplet similar to George Harrison's Black Bird so I get a feel for the neck and the fret board quite a ways up. Let's me know if the frets are true, if the the treble is solid, and if the bass and treble blend well.

On a 12-String it is usually Huddie Ledbetter's Good Mornin' Blues.

Roger in Baltimore