To copyright a song, you must put the song into a tangible form, such as on paper, CD, or a flash drive. Next, register your song with a third party that provides a time-stamped registration certificate. Keep a copy of your registration certificate in case infringement occurs. You can find more information here: http://ezinearticles.com/?What-You-Need-...

There are a couple of ways that you can copyright material. The first way is called the poor man's copyright and that is when you make 2 recordings of your work and you keep one opened and seal the other one. Then you send the sealed one to yourself and don't open it. The sealed one will have a time and date stamp from the postmark that will serve as a copyright. The other way, the legal way is to make a recording of your work and send it to the Library of Congress.