Three simple rules for great phone calls in music radio:

1. Have a clear ending in mind.  ‘Real’ people can be entertaining… but not all that often.
2. Let the caller finish his sentence before you jump in.  If two people are both talking at the same time, it’s hard to make out what either one of them says.  You’re going to edit the call anyway, so be patient.  That makes for good audio.  (If you’re taking live calls, that’s like rolling a grenade into the room.)
3. Remember that to the listener, it’s a conversation.  But to us, it’s a sound bite.  Do a nice, compact setup (or reset), hit the call, take the “out.”