My recipe file is organized in a way that I have found makes the most sense for me - mostly in the order of the courses served at a meal; ie, the order in which foods should be eaten for maximum enjoyment.
I originally learned about the order of courses in a traditional meal when I was in fifth grade, in beginning French class, and I have never forgotten it, surely because this lesson spoke to my gastronomical soul.
Even at the tender age of 11 years old, I understood how important it was, also, to drink the correct beverage with each course. In this picture from my old textbook, by Mauger, the various wines are illustrated according to bottle shape - something every 11 year old needs to know! At a young age, the die was cast, and I would forever be enamored with the French sense of organization a table.
The desserts section of my file, has lots of subdivisions, as I love patisserie. I have separate categories for Christmas (huge in my family's culinary annals); Valentines Day, Easter & Tea Parties; what to serve at Weddings, etc. This way, I can find always what I need in no time.
Sometimes, I just spend an hour or so looking through these files, getting fresh ideas and tweaking my memory of forgotten recipes and pictures. It's like reading a book on decorating. After time, I have new ways of looking at and thinking about old ideas, so that even something I've seen several times before becomes suddenly new and interesting. Going through my files is a great way to stir up my brain and get my creativity flowing.