Plagiarism occurs when you use someone else's ideas without giving them due credit. You can use other people's ideas provided you acknowledge where you got your information.
It is very important to cite the information that you use for your papers. As an author you are responsible for the references you include in your paper. Citing information accurately not only allows your professor to locate the information you have included; it also adds to your credibility as a researcher and writer. Above all, it helps to avoid plagiarism which is a serious offence.
Check Purdue's Online Writing Lab (OWL) for additional help.
Citation Game from Williams College
This is an excellent citation learning game that tests students skills in the follwining styles: ACS, APA, Chicago, and MLA. Try it - it's fun!
Citation Game from the Trio Training Team, University of Washington
Another excellent game where you need to drag and drop citation parts in the correct order for APA and MLA styles.