How soon can you register a trademark?

I am working on a book and as well found a very nice domain for it. I did some searching and it appears that I may have a chance at registering a trademark.

I was wondering how early on in the process I can try and register one? I would like to apply for it before I publish. If I have the site online already, can I just go ahead and send in an application and see what happens?

Are you sure that you don’t mean copyright instead of trademark?