The concept of fair use applies only if the use is for the purpose of commentary, criticism, classroom use or academic or research projects. Even if your purpose for using copyrighted quotations is one of these, be aware that an appropriate purpose does not by itself establish that your use is "fair."
Balancing Test: The Four Factors
Four factors are weighed when determining whether a given use of quotations from a copyrighted work is "fair." The unfortunate result of this balancing test is that there is no clear line between "fair" and "unfair" use--you only know for sure once you have been sued for infringement and have either won or lost the case. For this reason, it is wise to err on the side of caution.
The "Pupose and Character" Test
The first factor to be considered is whether the use is for profit or nonprofit purposes, or whether the use serves a redeeming social purpose (such as parody of the copyrighted work). Although nonprofit usage is generally viewed more favorably, a profit-oriented use that is judged to have social value--such as the advancement of progress in artistic endeavors, might also be viewed favorably.
Nature of the Copied Portion
A copyright is designed to protect exclusive rights to the expression of an idea, rather than the idea itself, in order to prevent private authors from claiming "ownership" of ideas to the detriment of society as a whole. Consequently, quotations that simply list facts without significantly unique expressive content are looked upon favorably even if they are taken from a copyrighted work.
Proportionate Amount Used
The smaller the length of the quotations used in comparison with the total length of the copyrighted work, the less likely the quotations will be judged to be infringing. For example, two lines from a 10-line poem are much more likely to be considered infringing than three lines out of a full-length novel.
Effect on Value of Copyrighted Work
If your use of quotations from a copyrighted work can be shown to have reduced the value of the work, you are much more likely to be considered an infringer. Your usage may be "unfair" if it makes it more difficult for the copyright holder to market or license her product, or if widespread similar use of the copyrighted work would have that effect. If your use is commercial, it will be up to you to prove that your use had no such effect. On the other hand, if your use is noncommercial, it will be up to the copyright holder to prove that it did.
You may quote from a copyrighted work as much as the copyright holder permits without fear of liability. When seeking permission, look first at the copyright notice printed on copies of the work, and contact the publisher seeking permission. Alternatively, there are many services on the Internet that can help you locate copyright holders for this purpose. You may be charged for the privilege of quoting from a copyrighted work.