Most of the citations you will see in databases, web services, etc., are produced authomatically using a computer algorithm. That means that if the data is incorrect, the resulting citation is incorrect. You have the final responsibility of checking that the citation is fully correct using the guidelines provided by your professor (or publisher).
Several websites have forms where you can fill in the needed information and get a formatted citation to cut and paste into your documents, like EasyBib, which does MLA, APA, and Chicago (APA & Chicago require an account off campus):
EasyBib: the bibliography maker.
EasyBib also has an account-based service, where you can store citations and notes, and format a bibliography to copy into Word.
And there are many more services available:
These services also let you set up a personal account, but aren't specifically supported by the library.
For large or long term projects, it's often useful to save and organize citations, as well as cite them in a specific paper. EasyBib has lots of tutorials to guide you when you starting your research, and makes it really easy to do Annotated Bibliographies. Endnote Web is free for student, staff, and faculty use, and is more advanced. Mendeley is free for anyone to install on their own computer, can be used offline, and is also more advanced. Zotero, another advanced tool, works best on your own computer, and lets you import directly from results lists. All but EasyBib have plugins for MS Word--the Endnote Web plugins are installed on the campus lab computers.
You can also get a personal subscription to Refworks, NoodleTools, or a personal copy of the EndNote software, which includes EndNote Web.