There are many things to consider when pursuing a career in genre writing. I’ve touched on a few general topics, but the more you delve into a specific genre, the more you learn what’s appropriate to that genre. These generalizations fluctuate between different genres, and they are only a start.
One thing to keep in mind is that genre is only a tool. It’s a tool for writers, it’s a tool for marketers and publishers, and it’s a tool for readers. The “rules” are important—understanding them is important. But there is plenty of room to play it loose. Serve the story, not the genre. Serve your career, not the genre. Your writing will be better for it.