NEVER LOSE SIGHT OF YOUR AUDIENCE.
I am acquainted with an author who wants to write a novel for young adults. So this individual writes novels with young adults in them. The problem? They're not young adult novels. A teenage character in a book does not automatically equal a young adult novel. The above-mentioned author, however, doesn't realize this, because the above-mentioned author has never read an actual young adult novel.
Which is a problem. OBVIOUSLY.
You have to know who your audience is--what they like, what they expect, what they'll tolerate and what they won't. And then you write for that audience.
Sometimes it helps to write to a single person. I always write my columns for my brother Jimmy. I try to make him laugh. I figure if he laughs, someone else out there might laugh, too. My colleague (such a fancy word!) Robert Kirby at the Trib has said he likes to write columns for his mother-in-law because she was (God rest her soul) easy to offend. And sometimes he likes to (surprise!) get a rise out of folks.
The point is--know who your audience is, know how you want them to respond, and go for it.