The Copyright Office website is quite user friendly, and has a lot of good information:
http://www.copyright.gov.
The Copyright office has recently started phasing out paper forms in favor of an online registration system. You can learn more about online copyright registration here:
http://www.copyright.gov/eco/faq.html.
Registration fees vary, but are significantly lower when registration is done electronically.
If you are not computer savvy, for now you can still request paper forms by clicking here:
http://www.copyright.gov/forms/formrequest.html
A few tips for submitting paper forms:
Forms should be two-sided
Do not use the US mail to deliver your paperwork and representation of your work, use a private deliverer such as FedEx or UPS
(The Copyright Office is one of the federal agencies that is still irradiating all incoming mail - a
process that can delay your registration up to a year!)
Another interesting and useful website to reference when navigating the legal issues surrounding copyright is Creative Commons:
http://creativecommons.org/about/what-is-cc