Never pay your electricity bill.
Fully two-thirds of your episode should be shot in the dark. It adds a film noir effect, a sense of waiting for something to happen, gravitas, and an overall sense of creepiness. Case in point: The X-Files. My first few experiences with episodes like “Squeeze”, “Leonard Betts”, and “Home” made the urge to shield my eyes a reflex action. And then I realized that I had seen far gorier things in delivery rooms and surgery floors without being the least unsettled.
Have at least one male/female pairing.
Tease the shipper contingent for a couple years, make the moment happen, and then either cancel the series after the tension has been resolved or make the relationship implode due to existing personality conflicts. Case in point: House and Cuddy on House.
Women should be able to sass her (their) male counterparts.
If there is no token blonde, there should be at least one with extremely long hair. She should also be stunningly photogenic, well spoken, super intelligent, extremely well paid, well dressed whether in the office or outside of it, wear mascara that’s both emotion-proof and water-proof, own a smartphone that looks like an iPhone but isn’t and has with a marathon battery life (24-48 hours), be stoic under great stress, have at least one ghost in her past, and be able to run like a gazelle in stilettoes. Cases in point: Kate Beckett on Castle, Jane Rizzoli and Dr. Maura Isles on Rizzoli and Isles.
Men and women should address each other by their last names.
The X-Files made it cool for the principal characters to call each other “Mulder” and “Scully”. They’ve become like terms of affection, and less like military utterances by a superior officer. In fact, if it weren’t for fansites and fanfiction to remind us (never mind the actors who portray these characters), we’d forget what their actual given names were. The “practice” has carried over to other shows. Case in point: Brennan and Booth in Bones.
Every principal cast member should be capable of cracking snappy one-liners, especially over a cup of coffee on a [very] early morning. Airtime is at a premium. Cram as many wry remarks in as you can. They’re easier to remember and recite over the dinner table than long, convoluted and tiresome monologues (unless you’re contemplating a career on Broadway or in politics). Case in point: Dana Scully, Fox Mulder, Walter Skinner, Monica Reyes, and John Doggett in The X-Files.