The purpose for citing is to let readers know that a specific piece of information you're providing has a source/author, other than your own observation or reasoning. In many cases, the strength and credibility of your work depends on the validity of your sources, the quality of the sources (especially peer reviewed journals), and your ability to represent those sources clearly without plagiarizing. Even if you fail to cite a source, or cite improperly, without meaning to do so, the consequences can be just as dire as if you did it on purpose, especially in academic and professional settings.
These are more specialized in nature than popular publications, but are not intended to be scholarly. These types of publications are aimed at experts in the field and/or keen amateurs, but the content focuses on news, trends in the field, promotional material etc. Research findings are not typically disseminated here - though they may report that a scholarly publication is forthcoming. These types of publications typically will contain more advertising than a scholarly journal - though it's usually targeted to the field in some way. Examples: Publishers Weekly; Variety; Education Digest
Quotations need to be introduced appropriately using a signal phrase or sentence rather than being "dropped" into the paragraph with no context. A dropped quotation is a quotation inserted into the text without a signal phrase. Note how the quotation in this example is "dropped" into the paragraph so that the reader is unsure who is speaking. Instead, dropped quotations must be integrated grammatically into the text through the use of a signal phrase. You can find more examples and solutions at these links: http:///faculty/ljonaitis/style_dropped_ ; http:///mitchell/node/29