Create an original saying, not a variation of another famous saying. "I don't need no stinkin' copyright attorneys," does not qualify as original. Yet a computer technician might use, "I'll make your computer bugs crawl away," for an original saying.
Embed the saying in a literary work that qualifies for copyright registration. Any piece of writing that could be deemed a poem or short story can contain the saying. Some poems are only two lines long, and they don't have to rhyme.
Register the work with the US Copyright Office (see Resources below) for all modes of registration. You can register online, fill out an online form to print and mail to the office, or request paper forms to be mailed to you. The copyright office encourages online registration and is phasing out paper forms.
Register for copyright online. Click the link at the upper right of the copyright office home page marked "electronic copyright office." Registration with (eCO) requires creation of a user name password, completion of a registration request form, completion of a registration form, a $35 credit or debit card payment and submission of works by file upload.
Register by mail with a fill-in form. Click the "Forms" tab on the top bar of the home page. Scroll down and click the "Form Co" link above the barcode. Click the "Download Form Co" link. Fill the form out on your computer before printing and mail to: Library of Congress Copyright Office 101 Independence Avenue, SE Washington, DC 20559, with a check for $45.
Register with paper forms from the copyright office if online or Form Co registration is not possible. Click the "Forms" tab, scroll down to "Registration with Paper Forms" and click the highlighted text "upon request," to fill out an online request form. Papers will arrive by mail to fill out and send with a $45 check to: Library of Congress Copyright Office 101 Independence Avenue, SE Washington, DC 20559.