Disclosure: I’m not a lawyer, nor do I have any specific expertise on these matters. I've compiled what I’ve learned over the years as an editor of online magazines and an instructor of online courses. I encourage you to take detailed questions to the experts in your own organization.
1) Copyright
Copyright refers to the right to control copying and other use of content that you create. On the Web, It might be text, graphics, music, video or something else. Even if you do not explicitly state that you claim a copyright, in the U.S. at least, you are considered to hold it for your own works. (See: Copyright on Wikipedia)
2) Creative Commons
Creative Commons (CC) is a type of license that sits on top of copyright. The variety of licenses explain the conditions under which the content can be used and how the content must be attributed. Content creators select the license that fits their needs and make a statement to that effect on the website, typically with a link to the text of the license. (See for example, the bottom of the Creative Commons home page!)
3) Attributing Content with a Creative Commons License
When republished or enhancing CC content, it can be unclear how to properly attribute an article or an image. I found this blog post on the topic quite helpful. I prefer to err on the side of providing more information about the source rather than less.
4) Crediting Source of Discovery
Bloggers and others who create on the Web often read about a news story or issue form another blog, a tweet, a Facebook post or via e-mail from a friend. It’s best practice when writing about the topic to cite not only any sources you reference or quote, but also to credit the publication or person that “tipped you off” to it. There are a variety of ways to do this: “H/T to John Smith” means hat tip to John Smith. To credit a tweet, a blogger might write: “via @johnsmith.” Podcasters can put such credits in the show notes or offer a verbal “shout out” or “thank you” to John Smith in the audio itself. There is no formal procedures for this sort of attribution, but one blogger has proposed a Curators Code.
5) Public Domain
Content in the public domain is free from intellectual property rights, most often, that means free from copyright. The creator may have removed the copyright, or it might have expired or be impossible to enforce. Most U.S. federal government website content is public domain as are many older documents and pieces of music. If content is in the public domain, so far as I understand, you need not attribute it from a legal standpoint. That said, I consider it best practice to attribute such content. In geography and GIS writing and teaching I often use maps from USGS or imagery from NASA, and attribute them.
6) Fair Use
Fair Use is a doctrine in the United States that grants an exception to copyright to use small pieces of works for specific purposes such as "commentary, criticism, news reporting, research, teaching, library archiving and scholarship." There are four factors used to determine if the use is fair or not. They are noted in the United State Code. This discussion and checklist from Columbia is a useful guide to the topic.
7) Permission
Any and all copyright or licensing requirements can magically disappear when the content creator/owner gives explicit permission to use it in a specific way. That permission may be given without a fee or there may be a fee. When a creator/owner grants permission, he or she may ask that you provide some type of attribution. If not, it’s best practice to make it clear permission has been obtained with language like this: “Reprinted with permission of the New York Times” with a link to the original article.
8) Adding a License to Your Content
If you create content, it’s up to you how you want to share it. You can be quite strict and hold a copyright and insist that everyone come to you for permission (and/or pay a licensing fee) to use the work. Or, you can share your creative work under one of the Creative Commons licenses and detail how the content can be used (only for non-commercial use, for example) and attributed. Or, you can put the content in the public domain. Those are just three ways to license content; there are other ways, too. Which ever you select, be sure it’s clear on your website which of these options you have selected.
9) When You or Someone Else Slips Up
Now and then someone will mess up and use your content without permission or without following the license you specified. And, you might use someone else’s content without permission or without the correct attribution.
What should you do if someone misuses your content? My advice is to respectfully let them know. My experience has been that more than 90% of the time they were not aware they needed to ask to use copyrighted material! (That's in part why I am writing this post.)
What if you receive an e-mail noting you misused someone else’s content? Check to see if in fact you did, and if so, apologize and offer to make it right either by removing the content, adding attribution or paying a fee.
10) Pass Along Best Practices
Many who read this blog are educators. We are role models for one another and for our students. We have a certain responsibility to lead by example. That means taking intellectual property rights seriously and trying to follow best practices when sharing content on the Web. I’ve been convinced lately that we need to teach one another as well as our students how these rights work and how to use them in practice. (If you missed it, see: Tales from the Web Literacy Files: Geo Edition)