Start early - the longer you put off that paper, the more tempting it will be to take shortcuts and plagiarize.
Keep track - you might have every intention of crediting a source, but you can't remember where you found it. Keep track of all the information you plan to use in one place, such as a Word or Google document.
When in doubt, cite - you can always ask your instructor or librarian if you need help.
This Citation Guide has directions on formatting your reference page.