What would be the proper way to alphabetize a name like this: Susan Jones Smith. In this case Susan Jones married Mr. Smith but decided not to hypenate her last name to Jones-Smith. Would you list her under J or S? (Jones-Smith would be listed under J)

Jones-Smith, Susan (Jones-Smith is one element and her last name.)

Smith, Susan Jones (Smith is one element and her last name.)

You need to know how she uses it. If "Jones Smith" is her last name then it is filed as "Jones Smith, Susan."
My rules of alphabetizing are as follows:
1. Single name: Smith, Susan J. (Jones is her middle name)
2. Hyphenated name: Jones-Smith, Susan
3. Compound name: Jones Smith, Susan

If you file compound names as Wondergirl suggests, you will not be able to find the file when Ms. Jones Smith calls to discuss something