Decide what kind of genre your series falls into---such as reality, drama, comedy or action. Remember that different guidelines exist for reality scripts versus fiction-based shows.
Come up with something fresh and original. Your show should not be too similar to another series---this could infringe on copyrights. Browse listings of all the shows that have ever been aired on the websites for each different network (see "Resources") to check for ideas that have already been used.
Create a log line: a brief overview of your TV-series idea that should only be a paragraph long. Make it to the point and captivating; this is what the TV producers read.
Register your log line with the Writer's Guild of America (see "Resources"). At a minimal cost, the registry lasts for five years.
Pitch your idea to a television network by writing a query. Include your log line and a brief overview of how you plan for the series to unfold. At this point, you do not need to submit a script, only an overview of the show and a summary about why you believe it should get picked up. Use this opportunity to sell your idea to the producers.
If the producers respond with interest, be prepared to submit a script for a pilot episode. Prepare your script so that each page is thirty seconds of the show. When pitching a reality show, submit an overview of an entire season.