What sort of things Should a comic book artist/writer copy-write?

I am an aspiring comic book writer/illustrator who has many different ideas for various stories and characters, I would really like to know what sort of things I should copy-write in order to protect my work from theft? what other forms of legal protection can i get for my ideas? what is necessary to copy-write and what isn't? What is the proper way to go about securing a copy write?