These are all excellent tutorials in citing sources. The "OWL at Purdue" tutorial is widely used and up-to-date; other tutorials have other advantages. If you want to learn a lot about citation style, you can read all three. If you only want to use one, you should probably use the OWL tutorial.
When you use MEDLINE through EBSCOhost, you can have the citation created for you! Look for the "Cite this article" icon to view citations in all the major citation formats.
Note the "envelope" icon and the "yellow sheet of paper" icon. The "envelope" icon lets you email the article and citation to yourself. The "yellow sheet of paper" icon pops up a little screen with MLA, APA, and other popular citation styles.
These citation tools are not perfect, but they usually have generally the right information in the right order. Be sure to confirm, though!