When you need permissions for class, presentations, publication, or Reserves use, these resources may guide you. The U.S. Copyright Office has a significant online service, as does the Copyright Clearance Center. When using an online service, often you can get quick results. Remember that electronic resources licensed by Case and OhioLINK are authorized via an acceptable use policy for shared educational purposes in a password protected environment. In many cases, the source you wish to share for your class scenario has a stable url that you can simply copy/paste into an email or on a course management site. In an online environment, check the web page for acceptable use or permissions online.
If your use is not considered a fair use, you need to get permission from the copyright holder in order to use the copyrighted material. Remember that fair use is the exemption, not the rule, and is not automatic for academic use. Also:
Plan ahead--online requests/responses can be quick but can also take time. A reasonable effort to locate the rights-holder is required. A refusal means that your use is not acceptable as planned, and a revision of your use may make your use fair. You can also conduct your own risk analysis in case of a refusal. Document all correspondence. Remember: permissions also can be fast, and free!
These are sample letters that should be modified for your particular situation. Brief, factual inquiries are easily read and are apt to be most quickly answered. Include a self-addressed return envelope if mailing your request. Online requests for permissions are becoming the norm, and brief email text is appropriate. Include a signature file on your email that indicates your title, department, and the university name.
Have a plan for this possibility, assessing your risk. You can change your use slightly (hand out copies in class but do not also post electronically, for example), or narrow your use if it was very broad and ambitious and then review Fair Use again. You might use an alternative work. Last, most common in the case of a copyright holder that can't be identified, located, or one that does not respond to your request even though you have invested great effort and diligence in doing so, you should review your risk of using the work. The evaluation is yours, based on the thoroughness of your search, and weighing your benefit against possible risk is critical. Good faith is not protection from liability.