You can use CC-licensed materials as long as you follow the license conditions. One condition of all CC licenses is attribution. Here are some good (and not so good) examples of attribution. Note: If you want to learn how to mark your own material with a CC license go here.
Here is a photo. Following it are some examples of how people might attribute it.
"Creative Commons 10th Birthday Celebration San Francisco" by tvol is licensed under CC BY 2.0
Photo: Creative Commons
"Creative Commons 10th Birthday Celebration San Francisco" by tvol, used under CC BY / Desaturated from original
This work, "90fied", is a derivative of "Creative Commons 10th Birthday Celebration San Francisco" by tvol, used under CC BY. "90fied" is licensed under CC BY by [Your name here].
Note: If you're at a point where you are licensing derivative works, go to Marking your work with a CC license.
You can visit the Saylor.org Introduction to Statistics course page to see how they marked it up directly.
A good rule of thumb is to use the acronym TASL, which stands for Title, Author, Source, License.
Title - What is the name of the material?
Author - Who owns the material?
Source - Where can I find it?
License - How can I use it?
Lastly, is there anything else I should know before I use it?
These best practices are based on actual CC license requirements. Noting the title is a requirement of all CC licenses version 3.0 or earlier, optional for 4.0. Noting the author, source, license, and retaining any extra notices is a requirement of all CC licenses. See Devil in the details.
If you have any doubts or questions, you can read the complete attribution requirements which are spelled out in detail in the legal code of every CC license, eg. http://creativecommons.org/licenses/by/4.0/legalcode#s3a. This chart compares the detailed requirements across all versions of CC licenses.
The license tells you to be reasonable:
There is no one right way; just make sure your attribution is reasonable and suited to the medium you're working with. That being said, you still have to include attribution requirements somehow, even if it's just a link to an About page that has that info. (More on different mediums below.)
As stated above, best practices for attribution apply as reasonable to the medium you're working with. For media such as offline materials, video, audio, and images, consider:
Video example 1: "Science Commons" by Jesse Dylan - see attribution starting at 1:52
Video example 2: "Video Editing and Shot Techniques: Study of jump cuts, match cuts and cutaways " video by New Media Rights - see attribution starting at 3:21
Audio example: "Down and Out in the Magic Kingdom" by Cory Doctorow read aloud. Mastered by John Taylor Williams - listen to attribution starting at 17:08
If you really want to go there, we have a document about marking materials so that they are machine-readable.
Also, several groups are exploring ways to make attribution easier and simultaneously machine-readable for the web. Here are some tools that have been developed: