You will want your research paper to be respected and credible. Therefore, after you identify sources relevant to your research, you need to determine whether they can help answer your research question.
There are four questions to ask when evaluating sources:
To determine whether printed or online published material provides appropriate information for you, review its table of contents, indexes, photographs, captions and diagrams, and read the first sentence of every paragraph, searching for words, names, concepts or images related to your research.
To support your research's legitimacy, you will want your sources to be experts who have considerable experience and training in an area and whose informed opinion can substantiate (or differ with) your point of view. (Just because a person is associated with a situation or idea does not make him or her an expert; for example, if you are researching medical waste, any person who works in a hospital is not necessarily an expert.)
Identify the range of expert perspectives, conclusions, opinions and approaches to your topic so you don't promote or rely too heavily on one source or point of view.
For example, if you are comparing the leadership styles of Ulysses S. Grant and Robert E. Lee, don't cite five books by Bruce Catton, or use six sources on Lee and only two on Grant.