Whatever system you decide to use, if it works, it’s the right one for you. After several attempts at creating a system, I found that keeping cards in vinyl window sheets, sorted by where I met them, is my ideal system. I’ve kept all the business cards I’ve collected in the past ten years in binders.
If a person appears not to be an ideal contact for me, I simply put their card in the binder in the section pertaining to where I met them without inputting them into the database. I find that I’ll remember the event more often than the person’s name. Having a date on the cards makes it much easier to pinpoint details about them. Later, someone might ask if I know a florist. I’ll refer to the binders and look up the event where I remember meeting a florist. Sure enough, the card is easily found because I don’t have to search through hundreds of cards and they’re in the order in which I met them.