Decide what genre you are writing for. Brainstorm important issues such as character lists, motivations, main event actions, and plot arc summaries. Map out ideas for first episodes, as well as general details and descriptions of the show, using a plot board diagram or post-it notes.
Brainstorm a great "hook" or "log line," which provides a brief summary of the show and pulls the reader in, as well as demonstrates the entertainment value of the overall show. For scripted works, an additional introductory summary for the show is usually less than five pages.
Assign a marketable and appropriate title for your series and episode. Make yourself familiar with conventions, formats, and page lengths of your chosen script genre, such as comedy or drama.
Format script. General guidelines for almost all genres require 12-point Courier font, as well as certain filming or set prompts. Add transitions and brief scene descriptions for all scene changes and openings in capital letters, describing time of day and whether the scene is outside (EXT. external) or indoors (INT. or internal). For example:
FADE IN:
EXT. CITY CORNER - NIGHT
Write action block or teaser after each scene setting in lowercase, describing actions in a few lines and introducing feature character(s). When a character speaks, capitalize and center their name, and center (lower case) dialogue spoken. Put in parentheses any actor cues while delivering dialog (i.e. "with a snicker").
Divide script into acts, in the same way that a play might be divided. Usually, act one is the longest in TV shows, and should end with a cliffhanger, as well as a centered title that reads: "END OF ACT ONE." Begin each new act with a slug line that introduces the main drama of that act, in the same way that you write an action slug line for each scene change.
Maintain the traditional page-length requirements of your genre; for example, half-hour sitcoms usually remain in the range of 25-to-35 pages, while hour-long episodes are around 50 pages. End episode with appropriate amounts of small-scale plot resolutions in order to maintain the internal structure of the episode, but also enough of a teaser to maintain viewer interest for the next episode.