There are many different approaches to formatting citations - these are called citation styles.
The most common citation styles are:
Your professor may require you to use a certain citation style for their class assignments, but even if you get your pick of styles, you must stick with the rules of that style and cite whatever is needed! Every citation styles has its own rules about how to format citations depending on what source you're citing and what information you've obtained about that source; that's a lot to keep track of, but you can easily look up these rules in the style manuals. Some of these manuals the library has in print in the Reference section and some of these may be online (click through the tabs below to see more).
Citation Generators like Citation Machine, Easy Bib, and Calvin's own Knight Cite can be very handy online tools that create citations for you automatically - they give you a form to put in the info from your source, you select the style you want, and they format everything! Or at least, they usually do... the free citation tools online are often the most basic, and they may not display things correctly every time, especially for online sources like webpages, where you can't find a lot of information to generate the citation. If you use citation generators, make sure you double check that everything is correct by comparing to the rules in a citation manual or guide, or you can visit the Rhetoric Center for help going over your citations (read more on the Where Do I Get Help? page)