Here's a sentence from article I was editing recently: "What's more — aside from a specialized curriculum — private schools are notoriously known for their smaller classrooms."
It's the kind of sentence that might not command much attention from the reader. It gets the job done, sort of. So this sentence could slip by without much notice. But upon closer inspection, it's a train wreck. And by looking at all that's wrong with it, we find some excellent lessons in how anyone can improve his or her writing.
The sentence starts with "what's more." That's a way of saying "additionally" or "also" or "on top of what I just said." There's nothing wrong with that, especially in speech and casual writing. But this isn't the kind of thing you see much in publishing writing, and there's a reason for that: It's inefficient.