Many professors prefer their students to use APA style when writing papers or posting on discussion boards. APA style is a style of writing and referring to scientific articles described in the Publication Manual of the American Psychological Association.
There are a number of web sites on-line that describe some of the basics of APA style. Usually, unless they say otherwise, professors are happy to see some APA style used, so it may not be necessary to get into all the intricacies of the style at first. Fortunately, the basics of the style can be learned quickly.
Once nice resource is by Yonnie Chyung and Linda Huglin of Boise State University and can be found here.
A briefer resource, that focuses on the basic of citing and referencing articles is by Scott Besshoat of Bellevue Community College. Click here for the overview.