Since scripts are formatted to a set of industry standards that dictate how action, dialogue, transitions, and shots are set up, writers in the movie and TV fields typically use screenwriting software that formats the scripts automatically, leaving writers free to focus on the story. There are no rules about which script software you should use, but Movie Magic Screenwriter and Final Draft are the industry standards. Another good choice is Celtx, which is free scriptwriting software (see Resources). Each of these programs automatically formats for plays, movies and TV scripts. Many TV shows have script formats specific to their productions, and Final Draft or Movie Magic Screenwriter will have templates designed for these shows.
Scripts for TV fall into one of three categories: two-hour movies, one-hour dramas or half-hour comedies. Each of these types of scripts has a different page count and different act breaks. For example, a half-hour episode runs 22 to 25 pages in two acts; a one-hour episodic runs 50 to 65 pages in four acts; and a two-hour movie requires 100 to 110 pages and seven acts. In most cases, a short teaser (the opening that grabs the audience) and a tag (the end scene that satisfactorily wraps up the story) are added.
Unlike a screenplay, scripts for commercial television have to be written around commercial breaks. As a TV writer, you'll want to stay aware of where acts they begin and end and, especially, where the commercial breaks are. The stories you write should end at these points with a cliffhanger that will bring your audience back from the break.