Say you have a character who’s a hardened detective, Detective Barebones. He must bring in Mr. and Mrs. Florestan, the parents of a missing teenager, to inform them that no leads exist in the case. Barebones brings them into his cluttered office and asks them to sit down. How would Barebones invite the Florestans to sit?
You would write:
Detective Barebones led the kid’s parents – a stiff-lipped older man with greying hair and his little, mousy broad of a wife – into his office. With one arm, he swept aside a stack of manila folders from his old desk chair, and with his other arm, he gestured to the couple to sit on the battered black and orange couch across from the desk.
“Sit down, Mister and Missus Florestan,” Barebones began.
Mister and Missus? Why write out “Mr” and “Mrs”? Well, because nobody actually says the letters M-R or M-R-S when he or she addresses another person. We sound the titles out: thus, “Mr” becomes “Mister”, and “Mrs” becomes “Missus.”
You might think that because this is a written dialogue, you wouldn’t have to write the titles out. However, your goal in writing dialogue is to write what people actually say, the way they say it. You would no more write “Mr” or “Mrs”, which no one says, than you would have Barebones address Florestan as “sirrah” (unless, of course, everyone in your story speaks Elizabethan English).
As another example, suppose you have a mad scientist with a degree from King’s College in your story. The scientist, Dr. Audric, is about to turn on the electricity that will bring his automaton, Clarabelle, to life. But his young assistant, who has scrofula, is in love with him and is jealous of Clarabelle. The assistant, Egberta, she wants to stop him. How would she address her erstwhile lover?
“Please, Doctor Audric!” Egberta cried, rushing for the switch. “How could you treat a woman so callously as to cast her aside just because of a little scrofula?”
Notice that I wrote out Doctor. Again, I did so because no one says the letters D-R when he or she addresses a mad scientist. Just as with the Florestans, you’d always address Audric the correct way – as Doctor Audric. Otherwise, you risk getting turned into a lab experiment.