When you use someone else's work without their permission, you face the prospect of a lawsuit for copyright infringement. Luckily, this unappealing outcome is not inevitable. Some awareness about copyright law, a little investigation, and a bit of flexibility can help you avoid claims of infringement.
First, you should consider whether the material you plan to use is protected by copyright. Many things are not copyrightable, such as facts and ideas, and therefore you can use them without worrying about infringement. Additionally, even works that qualify for copyright protection will eventually fall into the public domain after a certain period of time. For more information on this topic, refer to the section on Works Not Covered By Copyright.
Second, if you've determined that the material you wish to use is protected by copyright, you should consider seeking the copyright owner's permission to use the work. You will first need to identify the copyright owner, and then request permission for your specific use. If you are told that you cannot use the copyrighted work, this doesn't necessarily preclude you from using the work. You will not lose the ability to assert that your use is a "fair use" even if the copyright owner refuses to give you permission to use his work. See the section on Getting Permission to Use the Work of Others for guidance on how to do this.
Third, the doctrine of fair use may make it legally permissible for you to use a copyrighted work without permission for purposes such as commentary, criticism, parody, news reporting, and scholarship. Whether or not your use is lawful usually depends upon how different or "transformative" your use is from the original. Refer to the section on Fair Use for more information.
Fourth, rather than directly copy the work itself, you may decide to link to the material, if it is available online, is sufficient and thus avoid potential copyright infringment claims entirely. The section on Linking to Copyrighted Materials explores the legal issues that might arise from linking to or using a link to embed other online works.
Another issue you may face occurs when the work is protected by digital rights management systems (DRM) or some other technology that controls access to the work. You cannot circumvent these access controls without the permission of the owner of the copyright, and no fair use defense is available to you. We address these issues in the Circumventing Copyright Controls subsection.
If you are dealing with a work that contains a DRM system, or if the work is not in the public domain and you do not believe that the doctrine of fair use covers your use of the work, you will need the express and specific permission of the person who owns copyright in that material. We will discuss the process of getting permission to use someone's work from making informal requests to seeking formal licenses.
Finally, the section on Copyright Infringement goes through the elements of a copyright infringement claim and also discusses the intersection of plagiarism and infringement.