There are no rules.
Just kidding. Of course there are rules. There are rules of grammar, plot, structure, etiquette and all manner of other aspects of writing and publishing. The problem is there isn’t one, single set of rules. There are many.
In plotting, you can follow Shakespeare’s five act structure or a typical three act format. Or maybe you want to extend your story to four acts, because there’s precedent for that too. Television movies used to rely on a seven act structure and some still do.
There are also different camps or approaches to writing. Maybe you’re a fan of Truby, Snyder, McKee, Hauge or any number of other writing teachers out there.
The problem with looking for a set of rules is that you will never find the perfect one. There are too many approaches and too many ways to tell a story for that to happen. The best you can do is read, study and learn from a wide variety of teachers and pick out the bits of advice that help you.
The only rules you must to know are these:
Story matters. It needs to make sense and engage the reader. It needs to evoke emotion.
Characters are your way to build emotion. People don’t get emotional over plot (although they do stick with a story for that). They get invested in characters. Only characters can make readers feel.
Grammar matters. Learn it. Spelling too. Don’t rely on programs or apps to help you either. You need to know the rules yourself.
Structure matters. It creates the framework for your story. What form that structure takes depends on you and your story.
Manners matter. Don’t be rude. Don’t act unprofessionally. Don’t show up unprepared or, worse, drunk or high. Don’t blow off your agent or producer if you are behind schedule or upset.
Deadlines matter. Publishing takes forever to happen, but that doesn’t mean deadlines don’t matter. They do. Every stage of a project happens with its own timetable. Don’t push deadlines and don’t miss them. It leaves everyone else in the chain with less time to do their part.
Agent/editor/publisher rules matter. The rules set forth by the person you are submitting to matter the most. If an agent asks for a query and three chapters, don’t send four. If they ask to see the entire manuscript as a PDF, don’t send a Word doc. If a producer asks for a spec script, don’t send a shooting script. Breaking these rules can get you eliminated before a single word of your book is read.
Creative rules are not absolute. They are flexible and meant to guide you in your endeavors. If they hamper your creativity or don’t work for you or feel forced, find something else that works.
Writing is a creative act. Learn the basics and then play. Focus on your characters and story. You will learn a lot by doing, mostly what not to do next time.