There is not an easy answer to this. It depends on what class it is for, what discipline you are writing in. The best thing is to ask your professor what style they want, e.g, APA, MLA, CSE, ACS. It will vary whether you are in the humanities, social sciences, or sciences, and it varies within each discipline, each department, even each professor will have their favorite style. There is no one format unfortunately.
On our research and course guides we often have links to the recommended citation format.
If you use RefWorks, Endnote, Mendeley, or one of the other citation managers, then you can collect your references while you do your research. When you come to write your paper, the software allows you to choose which citation format (or style) you require and it formats your references into that style for you. It's great!