I just used a double-sided card box to store all my NPC/monster cards and the PC actions cards as well. I wanted to do the exact same thing for my NPC/monster actions cards as well but I am finding this task to be a tad more difficult due to some action cards being used by several different monster types. I had originally wanted to classify them similar to how I did my monster cards.....Greenskin, Dark Elf, Giant, Troll, Chaos, Beast, Beastman, etc. but the fact that some of these action cards are used by several different types makes this somewhat more difficult.

Those of you that have stored away and segregated your NPC/monster actions cards, how did you do it? What were your categories?

Thanks in advance!

I store them alphabetically and use the reference sheets that roam the web to find the corresponding actions for my creatures.

Monster cards and monster action cards, divided by type, plus elastic band. BAM.

I use the same division as the fan-made document. I've placed all cards in 9x9 plastic sheets organised by creature type and after each creature type comes their general action cards. Works a treat.

Here is a 4 pocket sheet that works well for nemesis sheets and career sheets. Below is the 9 pocket "trading card size" sheets. The 9 pockets are nice for several reasons: 1) You can put your monster and all his action cards in one sheet, 2) You can write on it with dry erase, 3) it's easy to prep an encounter (not as easy as if it was on a single sheet in a monster manual, imho, but this is your next best thing if you use cards)