As of March 1, 1989, the copyright warning does not have to appear for a work to be legally copyrighted. However, it is a good idea to remind people of your copyrights by including a statement such as:
Copyright © 2008 [your name]
Copyright © 2009 [your name]
unless otherwise stated
Consider adding a statement that specifically grants permission or restricts use, such as:
"Permission is given to copy this work provided credit is given and copies are not intended for sale."
"Use or inclusion of any portion of this document in another work intended for commercial use will require permission from the copyright owner."
See these examples in the Creative Commons
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.