DON'T FORGET THE BOOKS!
In any research you're conducting, it's a good idea to check to see if a book has been written about it. If you can find a book on the topic -- or on a particular company or issue or economic phenomenon -- you'll get a great grounding in the subject by reading the book or even selected chapters. When you search the catalog, individual book chapters (for newer books at least) can be located too. Take the time to do the reading up front, and it will be that much easier to do the writing later on.
Use the Library Catalog to search for books on a particular business, economics, marketing, advertising or a related topic. Make sure to note which location the book is found in.
If you are not having much luck with the keyword search, you can use a "Subject" search by choosing that tag from the drop down menu on the main search page to hone in on a specific topic. This can be tricky, but here are some examples of terms you can use (the links will take you directly into the catalog with the search results for these subject terms):
Citing your sources properly -- yes, even the charts and graphs you reuse from other sources, and the statistics you quote -- is important and required.
Purdue University's OWL Writing Lab Citation resources are the best ones out there on the web. Generally, Business & Economics courses require that you use APA citation style. Detailed information on both in-text references and "works cited" pages is available here.