A, B, C Storylines and Recurring Storylines
When writing for TV, it’s critical to create multiples storylines that interweave to create each exciting new episode. Commonly, the protagonist’s story is the A story (the main one), and then there are B, C, and other stories that can relate to the supporting characters, and even to the protagonist (as a subplot that he/she deals with in each episode). It’s important that all of these stories connect in one way or another, normally through the theme that’s being dealt with in said episode. The stories don’t have to physically connect, but it benefits your story if they are connected through something deeper being discussed that week, i.e. the theme of the episode.
A show can be episodic (each episode is a stand-alone episode) or serialized (the storyline continues), but regardless of that, each episode needs multiple mini storylines—half-hour shows need around 3, and hour-long episodes need 5-6. But what also makes a show great is having running gags or storylines that fans of the show can relate to and recognize, and that makes them say: “I know this show.” For example, every fan of “Friends” knows what “We were on a break” means. When referenced in other episodes, they don’t need to explain the original episode—fans know what they’re talking about, and it makes for an even bigger inside joke within the show. It’s part of the little details that you as a creator of a show need to think about in order to create a wide, rich, unique and believable world that makes your characters flourish and engages your viewers to keep coming back season after season (and even to re-watch once your show reaches sindication). So when you sit down to write your pilot, think first about the theme you want to tackle, then put your characters into the story, and start imagining how each of them could deal with said theme—that’s a great way to start coming up with all of your storylines!