Interviews
Generally, you can use material from any interview you conduct, including direct quotes, without securing a signed release if the circumstances and your notes clearly reveal that the source knew you were conducting an interview for possible publication and did not indicate intent to restrict your use of the material. Otherwise, ask the interviewee to sign a release.
Facts, Information, and Ideas
Generally, you may use facts you obtain from another work. However, note that copyright encompasses the format, organization, sequence, and style of presentation, as well as the sense or feeling of the original. When paraphrasing, even if you do not have to request permission, always give credit to the original source.
Public Domain
You do not need to obtain permission for materials that are in the "public domain." This includes all official U.S. government publications, as well as any materials for which the copyright has expired.