Generally, for beginnings you can keep the drone in the bum-titty even when it doesn't go with the chord. It just drones on and on regardless, and doesn't seem to do too much damage to the music. Eventually, if you shift to more varying clawhammer modes (a.k.a. melodic clawhammer, although someone is bound to comment that the asociation of Melodic and Clawhammer is an oxymoron) you will find yourself dropping the third note (in other words bum-tit, although I'm reluctant to write that lest someone make another anti-banjo coment). For my money, you can't do better than Seeger's How to Play the 5-String Banjo for starters.