I was taught that when you file the general rule is nothing comes before something. For example - Robb, P. comes before Robb, Patricia. But my teacher in highschool always used to say, "When in doubt, look in the phone book". The phone book is filed alphabetically and you can always use that as a reference. Although if you look at the attached PDF1 you will note that they don't agree with my teacher on the phone book idea.
1 INFORM Records Management News, Alphabetic Filing Rules, p. 5,6, http://www.filingdepot.com/inform/INFORM%202005-1.pdf, (accessed October 3, 2007)