Registry and Copyright

Hey guys,
I was wondering if anyone knows what is involved with setting up copyright protection on your photos. Is it just a matter of posting your name and a copyright symbol on the photo or is there like a registry that they need to go through? I would just hate the idea of putting a bunch of work into stuff and having it copied off the internet and then being usable. I have heard of things called watermarks but i dont really know what that entails.

thanks
Josh