Writer rule of thumb: You have to have one sample. You HAVE to. You should have more, but that's the bearest of minimums. Whether that's a play, a short story, a pilot, a feature or something else. You must have a piece of writing that's your calling card if you want to be hired. Most showrunners will want to read something original. Pilots, plays and features scripts are your best bet. Some are willing to read short stories, graphic novels, specs & other material. But pilots and features are where it’s at. Make sure they’re in good shape and ready go.