Sometimes, the fields available do not allow the finding and sorting that is needed.
Creating fields for these purposes are created. Often they are separate calculation fields that combine two fields into one.
Summary fields are the most common solution. The fields are often not seen by the user.
This is a simple article about sorting with a demo file. http://www.dwaynewright.com/filemaker-thoughts/2010/9/13/sorting-on-multiple-fields.html
Manually making a list or report on how you want to view the records can help define the required fields.