Some shows, such as the various Star Trek series, do accept unagented submissions, but they are in the minority. Some shows have intern positions which can provide valuable experience and access for the aspiring writer. In any event, the most important initial advice for any writer is to actually watch the show to acquire an understanding of the relationships of the characters. A writer must focus on the series regulars and the existing sets. Remember that hiring extra actors and building new sets costs money for the series producer, who will toss your script in the trash after reading the Ben Hur-type spectacle you have written into the second scene.
Many television shows publish submission guidelines.
These guidelines set forth not only the backgrounds of the characters, but also tell the writer how to format the script. Unlike movies, television shows have a very specific format which is largely dictated by the insertion of commercials. Most television production companies employ readers to evaluate the scripts that are submitted by outside writers. The coverage is a written synopsis and evaluation of the script. Even with shows that accept unagented scripts, it is important to know that in most cases a script will not be bought outright.