Well, course, there's this section which is where this question belongs:
http://www.backyardchickens.com/f/13/predators-and-pests
There are lots of answers to your question, but most of them start with making the coop Fort Knox. Chicken wire only keeps chickens in, not predators out. Welded wire or hardware cloth can keep predators out. And you may have to bury wire around it and the run, too. A cover over the run helps. Just a quick rundown, knowing what predators you do have helps. But posting in the section above will be more helpful, plus reading the stickies in that section.