Before applying Fair Use to an item you wish to use, you should first consider all other options available for using an item that may be covered by copyright.
There are specific statutory exemptions for use in:
Live classrooms -- Section 110(1)
Virtual classrooms -- TEACH Act -- Section 110(2)
There may also be express permission to use it. Libraries obtain permission for use of articles and images in the licensed databases. A single or blanket license from the Copyright Clearance Center. There may be a Creative Commons license available for the item.
There may be an implied license if you are linking or just looking.
The work may be in the public domain
It's a little long, but a great parody of copyright and fair use!!
Sometimes an item can be used without permission of the copyright holder if it will pass the Fair Use evaluation. There are four factors to consider when you evaluate an item for fair use:
The purpose and character of the use
The nature of the copyrighted work
The amount of the work you will be using
The effect of the use upon the potential market for the copyrighted work
You should also make sure that you are using the item in good faith.