We don't often find dialogue half that bad. And, in my own opinion, that's a goddamned crying shame. More such inspired lunacy would help us forget the bland chatter spewed by cardboard cutouts in book after book.
Now, if you Google the words bad dialogue you'll find plenty of posts on the subject. And some of them offer some excellent tips: avoid over-use of adverbs in attribution (he said robustly/hurriedly/passionately, etc.)...don't make dialogue do the work of careful exposition (John, could get me the brandy you've always kept in your rolltop desk's second drawer except for eight months after the death of your third wife, Estelle, the church-loving nymphomaniac who loved Mike Hammer novels?)...try not to sound like a music store geek emulating Tarantino (You friggin' love toy-lovin' Wop, I'll have a Big Mac with double the sauce, then groove my bop around Jay-Z and pistol whip your useless Dick, you Gaga-porkin' loser!)...
A writer who slavishly follows these rules and paints by numbers carefully will avoid such howlers as the one that I used as a headline. But nine times out of ten we'd have been better with a howler instead of the drivel we're served. Instead of offering a hundred examples of things to do or avoid, I propose two general rules that can help spare us no end of boredom:
1) Follow David (Rambo) Morrell, who advised writers to 'Enter a scene late and leave early.' In other words, cut to the chase and get right down to business. Likewise with your dialogue.
Let no account of a phone call include the usual opening pleasantries: 'Hello?' 'Hi, John, this is Joe Bob.' 'Why, JB, you old scoundrel, I haven't seen you in a dog's age.' 'I know, how're Betty and the kids?' Etc. BORING! Either skip the pleasantries completely, cutting to the chase: "I need to see you," I said when he picked up the phone. Or: "After a short round of civilized chat, I said: 'Do you still want me to kill her?'
Or let's say the characters do meet for lunch. Spare us their seating and banter while they order and wait for the food. Try: ' By the time the food came, we'd grown hungry to figure the best way to murder his wife.'
2) Our characters are more likely to sound like real people if we consider the emotional content of a scene. If every scene should move a story forward, so should every line of dialogue. Something's happening if it is doing its job. And real people are affected when things happen around them or to them. It must always advance the story--and never simply supply information.
Best example: In a key episode of Breaking Bad, Season 1, Walter White has agreed to 'take care of'' the surviving drug thug chained up in his partner's basement. But Walter still hasn't broken bad completely yet and is desperately searching for a reason not to kill the guy--who'll pose a real threat to Walter's family if he lives. Throughout the episode, Walter flashes back to an apparently banal conversation with a fellow teacher about a weird chemical equation: how all a corpse's body parts don't add up to the live person's actual weight. Could the missing part be the human soul? A moving question since Walter, as we knew him, is quickly disappearing from one show to the next. BUT WAIT: Walter dropped a plate while serving the drug thug a sandwich, then threw the pieces in the trash. Remembering the dialogue about the missing part leads him to remove all the plate's pieces and try to reassemble them. He is horrified to see that one piece is missing--held by the drug thug, who'll use it the next time White comes close.
And so it goes, and should go: even the simplest dialogue, if packing emotional content can shatter us as well as Shakespeare.