Consider such factors as the date of the material, the reliability of the person or journal or newspaper reporting it, the likelihood of a person's being knowledgeable about, or present at, a reported event, and so on. The least reliable sources are encyclopedias, secondary compilations of documents, quotations of quotations, prefaces, introductory surveys, or chapters in broad, general texts. More reliable, as a rule, are original documents, firsthand accounts, the work of original researchers or thinkers or compilers who first printed an idea or a research report or a statistical table, and people who are experts in a specialized field, not writers of some compilation such as an introductory textbook or a popular magazine account. If you need help evaluating the worth of a book, check the Book Review Digest to see how others have viewed it. If you need help selecting from several possible sources, see whether there is a recently published selected bibliography or review article.
Many students quote too much.
Avoid long, dull quotations, especially of material considered common knowledge. When you quote material directly, you have an additional responsibility besides the footnote. If the quotation is shorter than four lines, use quotation marks and just include it right in your paragraph, making sure that it fits in smoothly. Remember to include both sets of quotation marks, at the beginning and at the end of the quote. If it is longer than four lines, then use no quotation marks.