I'm working on a pilot.
I should clarify: I'm working on a spec pilot.
Working on a spec pilot means you have an idea for a TV show and you write a script of that idea and while you have an idea of where it could "fit" (you should ideally always have an idea of where it fits, even if it's sort of a well-it's-a-high-school-girls-MTV-but-could-be-ABCFamily-ized-or-oldified-to-Lifetime-but-maybe-it-could-also-live-online) but you don't have a buyer. You have an idea and a possible home but the chance of you actually ending up in that home is that sliver of light between slim and none.
Speccing a pilot is the most freeing (total! creative! control!) and a waste of time (no! one! will! buy! this!) but it gives executives and producers and idea of your "voice" and it gives you the opportunity to flex those writing muscles that easily atrophy when you're writing for other people's characters week after week. (Note: I love writing for other people's characters. Hire me!)
I'm not a Chuck Wendig. (Imagine Warren Ellis, but cuddly.) The dude is a fucking machine. (A writing machine, not actually, you know, a fucking machine--Jesus, this is what happens when I sit down to write something longer than a Tweet. Chuck, I blame you.)
Yes, that's mostly an excuse to not write. But the writing for me is the easy part. I hate it, but writing for me is simply turning off my brain and getting out of the way. No, the thing that takes the time is the jigsaw puzzle. How do these characters fit together? How does this story fit together? And how will this story continue, week after week?
Because even though the chance of your pilot being purchased/optioned by anyone is less likely than a unicorn crapping sparkles in your front yard, you still need to write something that lends itself to continuing. To characters that you want to spend week after week with. To situations that aren't contrived but still are familiar enough to circle of comfort zone of the everyday viewer. If a Producer or Executive - who reads thousands of scripts in their lifetime wants to not only continue reading your script, but wants to know what happens next? That's what gets you the meeting, the job, the script option. (Which- having personally experienced - is awesome.)
For me, a pilot starts when I have two people having a conversation in my head. It's always two people. In the writing, it may branch out to more, but it's always two people taking about something dumb. I take those dumb conversations and make notes of them on my iPhone. In TextEdit. Snippets of dialogue grows like mold and out poops a situation.
There, buried under the poop, is are the nuggets of the story. Sometimes it's right on top so you don't have to dig too far and the pieces fit together perfectly. But sometimes you gotta dive in and get your hands dirty, and you try so hard to make all of those little shitnuggets fit that they disintegrate in your hands. Which means you were looking in the wrong pile of shit, so exhausted and filthy, you start over.
Now you get to take your characters, those assholes you started with, the ones who are taking up space in your brain where you're supposed to remember birthdays (thank you, Facebook) and Raising Arizona quotes ("This here's the TV. Two hours a day maximum, either educational or football, so as you don't ruin your appreciation of the finer things.") and you drop them in your story like a couple of Sea Monkeys, and it's up to you to make sure they survive.

Right now I'm digging through the shit. Hopefully there'll be something good in there.
We'll see.