Know the rules. You can use an author's published or unpublished material without permission, under limited circumstances such as public domain. Under public domain, published material no longer has the protection of a copyright.
Find materials that fall under public domain. You can use any copyrighted material first published in the U.S. before 1923 without permission. Also, you can use any material created from 1923 to 1963 that no longer has copyright restrictions.
Seek permission when the author's work is protected by copyright. Contact the author to obtain permission to use the work in your text. To find out the copyright owner, look at the work or contact the U.S. Copyright Office.
According to the U.S. Copyright Office, under fair use, you can incorporate a limited amount of an author's protected material in your text without permission. This typically consists of using quotes in scholarly papers, journalistic articles like news reports, or criticism or commentary.