Remember that if your use of an item meets the fair use criteria, you do not need to seek permission or pay a fee!
Seeking Permission from the Copyright Holder:
In seeking permission, a first step can be determining if the copyright owner will allow you free use, or permission, to use the material. This requires contacting the copyright holder and explaining how you plan to use them. Many individual authors and some scholarly societies will allow you to make copies, post digital copies on an internal Web site, or even repeatedly use the material for free.
What's the catch? The biggest problem is finding the real copyright holder. Most authors listed on an article or in a book do not own their materials and cannot give you the right to make copies or distribute them, even for educational purposes. Publishers of books and journals usually hold the copyright.
To seek permission you have to identify the correct copyright holder by checking the back of the title page or looking at the journal issue to see if there is a statement. Then you must contact each copyright holder for each item you plan to use. It sounds simple, but dealing with and waiting for responses from authors and publishers can be time consuming. For example, there may be several authors on a paper that requires contacting each author, or the publisher may have merged with another publisher. Some publishers do not have easy systems for seeking permissions, and some refuse almost all requests.
Seeking permissions can save you money (no royalty fees), but may cost you a lot of time and effort.
Another way to seek permissions and manage possible royalty payments is to work through a licensing agency such as the Copyright Clearance Center (CCC), which represents a number of publishers. The advantage of such a service is that the process for requesting use from several different publishers is more efficient and there are easy systems for paying the royalty fees. It is also faster than contacting individual publishers and authors. However, there are usually fees for using the service, in addition to the royalty charges, and you may be giving up your fair use rights to use the materials for educational purposes.
How often a work is used is NOT part of the copyright law, though some publishers believe you should seek permission or pay a royalty fee for repeated use of copyrighted works. A safe practice is to seek permission for repeated use, especially if the use is over several years, but it is NOT stipulated by the copyright law.