"You can only succeed, if you do everything everyone else tells you not to do to succeed."
People can tell you what you need to do in order to make a best-selling book or a winning film. Your book or movie may be famous, a big hit, a mark of success, for a little while; and then it will be entirely forgotten. Think about it: can you name the #1 New York Times Bestseller from fifty years ago? Twenty years ago? Ten years ago? Five years ago? Two years ago? Who cares anymore? But, can you name a book that was written hundreds of years ago, maybe wasn't too famous in its day, but is still read and appreciated today? I could name lots. I'm sure you could too.
To really succeed, I think, you have to break away from the conventional, present set of rules for how to become a "best-seller" (those rules are always changing anyway) and write something that transcends your day and the current fads that go with it. How do I know? I don't know for sure, because I haven't experienced anything like that before (the extent of my published writing "career" has only been one newspaper, one magazine, and this blog itself); but I know that other people have experienced this.
Take J. R. R. Tolkien for an example. People told him that his writing style was not publish-worthy; it was not the way things were preferred to be written at the time; he should change it; yada yada. (One thing that was criticized was the way he switched between characters, not writing things chronologically.) But what ended up happening? He became the father of the modern fantasy genre. "Tolkienesque" became a word to describe the genre he helped begin.
What if he had written the way people told him to? I don't know. Maybe he would have ended up being one of those best-selling authors from decades ago that have been completely forgotten.
Now, there is of course a limit to this. In a general sense, we definitely should listen to the advice of writers who are published or more experienced than we are; they know what they're talking about! (I, on the other hand, do not. *Smile*.) They might say you need to have round, believable characters. Okay, we should probably listen to that advice. Or they might say we need to have a strong climax, or a grabbing first chapter, or that we should use strong verbs and adjectives. Okay, we should probably listen to those bits of advice, too. Just don't follow the guidelines too religiously. Develop your own style. Shout with your own voice.
Be a rebel.