So, like many writers, I have a sort of soundtrack for each novel as I work on it... music that gets me in the right mindset or relates somehow to the action of the scenes I'm writing. A song, after all, is just another way to tell a story, and so it is no surprise that many writers find themselves moved by lyrics. And what moves you, moves your characters, yes?
Well, however moved you may be by those lyrics, you should make every effort to keep them OUT of your novel.
What you may not realize is that, just as you hope your novel will be, the lyrics are copyrighted. And if you want to include lyrics to which you do not personally own the rights, a publisher would have to get permission from the copyright holder, which is an added hurdle and potential expense.
Titles, however, be they song titles or book titles, are not copyrighted. Which, incidentally, means there is nothing legally stopping you from querying "Gone with the Wind" or "Romeo and Juliet" (but plenty of logistical reasons, natch. And not exactly the way you want to get an agent or editor's attention).
Another copyright wrong involves fictional characters that you yourself did not create. In other words, however fascinating your novel about the adventures of little Albus Severus Potter or how compelling the high jinx that ensue when the Marvel heroes meet the crew of the Enterprise, it's not publishable, because you don't have the rights to those characters.
In a related wrong, you'll probably also want to avoid fictional stories where main characters are real people. Meaning, that novel where Princess Diana travels back in time and causes her own deadly crash will need to stay trunked. ;)
What other copyright traps can you guys come up with?