Before you even begin to research your topic, think about how the sources you encounter could help you make your argument. How you plan to use a source will affect how you will evaluate it. Not every source must directly support your thesis.
Sources can have various functions in a paper. They can
provide evidence for your argument
lend authority to your argument
offer counterevidence and alternative interpretations to your argument
provide background information or context for your topic
explain terms or concepts that your readers might not understand
For examples of how student writers use sources for a variety of purposes, see the sample papers in MLA, APA, and Chicago (CMS) format.