I recently discovered on Amzon a most useful wargaming accessory.
These are blank, playing card sized, plasticised cards. You can use any felt-tip pen to write on the cards and it takes immediately without smearing.
I am using the cards to record rules for games in development. When the game is finalised the cards can be sorted and transferred to a document.
You can see here red cards for combat, green for movement and black for general game rules.
My original purchase was intended to use the cards for unit records in a game.
I think they come in packs of 200. I bought 1000 for £13.98.