If, for instance, you are to submit a manuscript for publication, you simply declare the copyright on the front page. (There is a book called The Writer's Market, which comes out every year, and summarizes publication needs; as far as I can tell, you just put a copyright and date on the thing and wait for anyone to argue.)
As such, the more people who are familiar with the work, the better. To some degree, the copyright is inherent. Look down at the bottom of the Sciforums page. You'll see a familiar phrase: "Portions copyright ... Dave Watanabe". I don't know about Canadian law, since I'm under the impression this is still a Canadian website, but in the United States, the implication would be that what we write is automatically ours, whether we declare copyright or not.
However, I am not an attorney and therefore cannot dispense official legal advice.
© 2004 Tiassa