These are lower than low tech things that can eventually speed retrieval-- very easy and has saved me minutes but cost me but seconds.
Simple x-reference: When you make a label for a paper that could be filed under different headings, make a label for the other ways you are thinking you might file it and add "see_____". Pop that on a folder but don't put anything in it. File as your usual a-z method. Very handy also if you are an inconsistent useer of such terms as: medical vs health, data forms vs record forms.
Parallel but comprehensive list- When making a file head label for an item that is one of a group of related items, print a second label at the same time, stick it at the top of a piece of paper, pop that paper into a file that has a more generic and encompassing heading, then you will easily have a file with a list of all the items in that category and it can readily come in handy. For example, say you belong to 23 organizations. You will have twenty three files, one for each one, and also a 24th headed "Memberships-all" and in that you will have 23 pieces of paper with name of each. Alternatively, if you foresee the need, you could put the label on notebook dividers or in your roledex. I put them on separate sheets of three hole-punched paper because I can then manipulate the order to my liking.
One final suggestion, when you type a label if it pertains to something that also has a number, such as a membership number, or account number, put that on or just under the label as well.