BOOKSBooks generally provide in-depth and lengthy coverage on a given subject, but because of the amount of time involved to write and publish, the information is not always up-to-the-minute. This is only a concern if you are researching a topic that requires the most current information available. If you are unsure of the merit of a book, consult a book review published in a professional journal of the given subject area.
Daily newspapers are a great source for information on current events, such as Middle East peace talks. Older editions provide day-to-day coverage of past events such as the oil embargo and the Manson murders. Because newspapers are outlets of mass communication, they are good barometers for reading the interests of the popular culture.
Like newspapers, journals are good sources for current information. Journals differ from newspapers in that many periodicals are professional in scope and are devoted to a specific field of study, such as Journal of Protozoology. Articles appearing in these journals are much more authoritative than comparative newspaper articles as most have very stringent review processes for submission. Compared to books, journal articles tend to focus on a specific aspect of a topic, and are less useful for general overviews or histories of a topic.
Book reviews are good indicators of a work's value to a given subject area, especially if you are somewhat unfamiliar with a given field of study. As always, consider the source of the review. One that appears within a scholarly journal of the field in which you are doing research has more authority.
The Internet is a great resource for getting current information on a variety of topics, BUT always consider the source. The commercial domain(.com) is less reliable than the educational(.edu) or government(.gov) domains. Also, check when the site was last updated (you can do this and check the source of the document by opening "document info" in one of the pull-down menus of your web browser). If the site was updated several months ago, chances are the information contained within is not reliable. The Internet is useful for finding information on associations and companies, but remember to pay attention to who has authored the web page.
U.S. Government documents are excellent sources of information on a variety of topics, such as business, science, law, criminal justice, etc. These primary documents, published under the auspices of the federal government, provide vital information such as census data, supreme court transactions, and federal rules and regulations.
Dissertations generally cover a narrow topic but do so in great detail. The authority of the work is generally without question as all are produced under the guidance of an academic committee within a university. To gauge the value of the information to a given field of study, check to see if it was published. A published dissertation has made it through the extra review process of a particular press, and therefore, it is likely to be more authoritative than a similar paper that has not been published.