i use a hilarious method that i should probably stop doing.. i took a white gift card i had, and marked off 5/8 inch increments on it, marking how many decks are left at each increment, so at the bottom it says 5, then 4 above that, etc, and i hold that up to the discard tray when i sit at 3rd base.. the reason i should stop is probably obvious, but one less obvious reason is this is a crutch for me, and i cant do this every round, so sometimes i have to guess based on 2-3 hands ago