I've been looking into this, and found a few variations: Mister, Master, Doctor, Parson. However, I'm still unsure as to which one(s) to use. Doctor seems fairly obvious, in that it should only apply to a learned man with a degree, but I'm even a little unsure on that. In my research, Parson seems to be a more casual/familiar term, and even a little derogatory in some instances.

Is there anyone out there who can set me straight on which forms of address to use and when?