To give credit and avoid plagiarism there are several citation styles established by scholarly communities. These different styles (e.g. "MLA" vs. "APA" etc.) tend to be discipline specific and your instructor will inform you to what citation style is required.
Citing Your Sources when copying text exactly, restating other's findings in your own words, and paraphrasing other's conclusions, ideas or interpretations.
Save time: note that Word has templates you can use for both MLA and APA citation styles!