For a good overview of this process, see the Library's guide to Requesting a Book not at UIUC.
(Note that we can obtain material from many other academic libraries in the state through the regular online catalog, I-Share, without going through ILL. When you obtain a book or journal through I-Share, it is not considered "interlibrary loan," since the transaction takes place within our own online catalog, even though the material may be coming to you from Northern Illinois University, Illinois State, or one of the other 130+ participating libraries.)
Need an article from a journal that the Library only has available in print, but don't have time to come in? We will deliver the article to your email inbox! Use the DocExpress service to initiate a request.
You can also place ILL requests directly through WorldCat. This is a "union" or combined catalog for thousands of libraries that share cataloging records. Note that you can search the title of a journal in this database to find out which libraries own the journal, but to identify articles in a journal, you need to use one of the article databases.