Copyright and Fair Use

Ok, I hang my head in shame because copyright is not something I know a whole lot about. I know it's in my job description, but I just can't seem to get a grip. I seem to put a lot under "fair use" and then not worry about it. That is the wrong thing to do! Here's what I learned (besides the fact that I'm most likely violating copyright without even knowing):

--Copyright gives protection for authors of original works.
--Anything you make is automatically copyrighted.
--Facts and public domain items are not copyrighted.
--You can register your own items for a nominal fee.
--Fair Use allows teachers and students the ability to use materials for educational purposes (not for recreation!). 4 points for fair use:
1. The purpose and character of use for education
2. Nature of the copyrighted work
3. Amount of work used
4. Effect of the use on the market place (Is it impacting finances for the author)

--Copyright Law for Teachers and Librarians (book) to find out what is classified as Fair Use?
--Creative Commons
--Digital Resources have 2 laws: (and this is where I start tuning out because I don't understand everything!)
Digital Millenium Copyright Act (gives rights to libraries for archival purposes)
TEACH Act (had to buy a copy/permission from the author to post & limited to class members only (password protected)

Can use images/video legally by:
-use online databases or another multimedia service (Discovery Ed Streaming)
-flickr (etc.) for creative commons licensing (for educational purposes)
-ask permission to the copyright holder
For free & available music:
www.projectplaylist.com
www.squidoo.com/freesounds
www.royaltyfreemusic.com
www.soundzabound.com

The more I learn about copyright, the more questions I have. Can I use just a portion of a song? Is it 10% of a book you can copy? Can I place images of books on the website? I might try the book I just referenced so I can find the answers...