THE RULES FOR WRITING SITCOMS. I have seen it pointed out that screenplays for movies are supposed to have a three act structure, but I have never noticed the three acts while watching a movie. Similarly, I have heard that television comedies are supposed to have three acts, but I have never noticed the acts when I am watching. It turns out that there is an accepted structure for sit coms which goes into much more detail than a simple three act division. This article in the Atlantic by Noah Charney spells out some of the rules.
A sitcom usually is 22 minutes long. There are three main acts, divided by two commercial breaks, with 3-5 scenes per act. This would mean that there are from 9 to 15 scenes in a show—which means that thee “scenes” are very short.
Each episode begins with the protagonist stating a goal or problem—this would be in minutes 1 and 2. Other parts of the structure are:
The Trouble (Minutes 3-8)
The Triumph/Failure (Minutes 13-18)
The Kicker (Minutes 19-21)
Around the 6th minute we might be introduced to a subplot (Story B). Story B would begin later and be resolved earlier.
Charney says that the jokes are often filled in later.