Fair use doctrine provides a set of guidelines pursuant to which researchers, educators, scholars, and others may use copyrighted works without seeking permission or paying royalties. Fair use doctrine does not provide a right to use somebody else's work, but presents a defense against accusations of copyright violation for people who reasonably believed that their use of a copyrighted work was fair use. That means that if your use is challenged, you will have the burden of proving that your use qualified as "fair use".
As a general rule, a copyright owner has the legal right to restrict the reproduction of a copyrighted work, and to demand royalties when copyrighted work is reproduced. The penalties for unauthorized reproduction of copyrighted work can be substantial. Accordingly, it makes sense to have a pretty good idea of whether or not you can defensibly copy part or all of somebody else's work without that person's permission, before violating copyright law.
Unfortunately, the determination of whether any given use is "fair use" can be complex. When evaluating whether or not the use of a copyrighted work is "fair use", there are four factors which must be considered:
What is the character of the use?
What is the nature of the work to be used?
How much of the work will you use?
What effect would this use have on the market for the original or for permissions if the use were widespread?
In most cases, if a court determines use to be fair under the first three factors, it will not revisit that determination based upon the fourth. On the other hand, if your use is found not to qualify under any of the first three factors, a court will typically examine the economic impact of your use as part of its ultimate determination. This essentially means that if a use is fair, the economic cost to the copyright holder probably will not shift the balance to render the use unfair, but if a use is not fair the economic impact on the copyright holder becomes a central point of focus for a legal action.
As you may have inferred, fair use is not determined by a series of simple "yes or no" questions, but involves a relatively complex balancing test between the private interest of the copyright holder and the public interest. No particular use, no matter how much in the public interest or how educational, will automatically qualify as "fair use".
When there is any doubt about whether fair use doctrine applies, you should consult with a copyright professional. This is particularly true where you have previously inquired with the copyright holder about your proposed use, and were denied permission to reproduce the desired excerpts of the copyrighted work.
The less commercial the use, the smaller the portion used, the lesser the import of that portion of the work to the whole, and the lesser the effect on the market for or value of the work, the more likely it will be that fair use doctrine will apply. The cheaper and easier it would be to license the desired portion of the work from the copyright holder, or the more valuable the excerpt to the work as a whole, the less likely it will be that your use will be determined fair.
The more fact-based a given work, the more likely it will be that "fair use" applies. You should exercise greater caution with more imaginative and creative work, as compared to compilations of fact.
In this context, images often enjoy greater protection than written work. Before copying an image that is not in the public domain, you may wish to investigate the possibility of licensing the image from the copyright holder. In the event that you proceed under "fair use" doctrine, your use is more likely to be later found permissible if you reproduce the image at a small size (such as thumbnail size). As much as possible, limit the distribution of copies of the images or excerpts of multimedia works.
A good rule of thumb for "fair use" is that you should avoid using more of a copyrighted work than is absolutely necessary to make your desired point. Exceeding the minimum makes it more difficult to argue that your use was in fact fair use. Similarly, as suggested by the examples above, do not reproduce only the most valuable portion or portions of a copyrighted work. A fair use evaluation weighs the value of what you copied against the value of a work as a whole.
Another good policy is to ask not just what effect your own use will have, but what would the effect be on the copyrighted work if similar copying occurred on a wide scale. If it is apparent that widescale copying of the type you propose would damage the value of the original work, your use may not qualify as "fair use" even if you are only making a few copies.
If you compete with the work you are copying, your use probably will not qualify as fair use. If your use will diminish the value of or market for the work, it also probably is not fair use.
Please note that for any use of somebody else's copyrighted work, you should provide proper attribution of the work by presenting the copyright notice from the original work, and provide appropriate citations to the original source.
If you are a student, or a staff or faculty member at an educational institution, your institution can probably provide you with a set of guidelines and perhaps even some direct advice on the propriety of your proposed use of copyrighted material.
Consider the use of sports highlight footage by competing television networks. The networks have a mutual agreement whereby they can air the highlight footage, in return for letting other networks air the highlights to which they have exclusive rights. Even though the highlights are short, they are the most valuable part of a recording of a sports event. To the extent that it might be argued that "fair use" applied, it would not be to the highlights, but would be to the routine play in between the highlights - the type of footage that doesn't make for compelling news coverage. Also, there are exceptions to the mutual agreement, which is why you will frequently find that highlight footage from Olympic events is broadcast only on the network which purchased the rights to broadcast the Olympic games.
Consider also a politician's memoirs. Often there are a few key passages in any such book, which contain the most revealing information, or the most interesting anecdotes. The publication of even a few key excerpts from such a book may significantly affect its market, as people who have read those excerpts may choose not to buy the book. This effect may increase if the publication is made from an advance copy, as opposed to the published book.
If it's Posted to the Internet, I Can Use It Without Permission
Publication to the Internet does not place the published material into the public domain. It may be easy to copy pictures, videos and information from the Internet, but that content is subject to the full protections of copyright law.
If I Don't Make a Profit, My Use is Non-Commercial
Although a court will consider whether or not your use of copyrighted material is a commercial or noncommercial use, that's but one of the factors considered in evaluating a fair use defense. Your profit margins are not relevant to the analysis of whether or not your use is commercial.
If I Am Not Trying to Make a Profit, Copyright Law Does Not Apply
Copyright law always applies. The Fair Use exception is a defense to an accusation of copyright infringement. It is very possible to violate somebody's copyright and to cause them significant damages that they can recover in court, even if you are making no effort to make money from your distribution of their copyrighted material.