1. Encyclopedias
2. Dictionaries 
3. Handbooks
4. Online Scholarly Databases
5. Book Catalog
6. Periodical, Newspaper, Citation Indexes
7. Essay and General Literature Index
8. Biographical and Book-Review Indexes
9. Concordances and Books of Quotations
10. Statistical Sources and Government Documents

Tip:  Be sure to consult the bibliographies at the end of the scholarly articles and books you find – there is a wealth of information there which can add depth to your research.

After you have become an expert at determining which areas will best meet your research needs, and have experience in working your way through the entire sequence, you will develop a sense for knowing which steps in this sequence might be useful for a particular subject.

In consulting these categories of reference sources, you will, in most cases, accumulate a wealth of information on the subject you are researching.  Eventually, you will have to make selections from the mound of information you have found, evaluating the information for its relevance, accuracy, and credibility.  To assess the reliability of information, you could consult reviews of the books from which you have gotten the information or you could check the reliability of the newspapers or magazines in which you found the information by researching the reputation and ideology they are known for.  In the end, you should have a variety of sources – A good rule of thumb is to have at least as many sources as the number of pages in your research paper.