As you're selecting your topic and gathering background information:
- Look at some subject encyclopedias like those I've suggested on this page.
- The journalism ethics sites at the left side of this page may give you some ideas.
- Also check the library catalog for books on your topic. Think in terms of broad searches like "freedom of the press" or "journalistic ethics" when you're doing catalog searches during this stage.
(I also suggest NPR's On the Media program, which covers interesting issues in journalistic ethics in almost every episode.)