Do Not Fuck With Your Fans

Your first rule. Your most important rule. Do not fuck with your fans. 

In a day and age of DVR's and TiVo's, of pausing and rewinding, of memorizing every line of dialogue and facial expression, your characters cannot say something or act in a way that will cause your audience to (ecstatically) jump up, point a finger at you, and yell, "No! Leonard would never do that! Sheldon would never say that!"

We are currently at a very sophisticated point in history with television shows. I am, of course, aware that I'm speaking of a time in which reality TV graces our screens in abundance. But I don't count reality TV as real. What I'm talking about are real, scripted shows that need talent in writing, directing, and acting (and much more, but we'll keep it simple for now). After Joss Whedon made character development, continuity, and story arcs relevant with Buffy the Vampire Slayer and Angel, we now, as an audience, pay attention to the people whose lives we tune into once a week. 

So your first rule: Do. Not. Mess. With. Your. Audience.

The way Steven Moffat did, in the seventh series of Doctor Who. The Doctor says, "I thought we might need a gang. Not really had a gang before." The Doctor has had a gang before, at the end of the fourth series. The gang of all gangs- Donna, Rose, Jackie, Martha, Captain Jack, Sarah Jane Smith, and Mickey. And no amount of crappy writing (Chris Chibnall) and showrunning (Steven Moffat) will ruin that.

You need to know your story and your characters better than your audience does. You better memorize every damn piece of dialogue, every traumatic experience, every tragic facial expression or flirty wink you've ever written, because your fans are doing the same. And for the love of all that is holy, do not fuck with your audience because they will leave you.