I write down some stuff on a scratch pad like tasks and little things i need to pick up. There’s something satisfying about crossing them off my list. Also when I plan a longer vacation where I stay in multiple places I need to write it out like a calendar with details for each day.

I use text files on my phone for longer term stuff. A Christmas gift list for ideas that pop up during the year, checklists for outdoor trips I plan regularly that i can send to others, a shopping list of fly tying materials (some are hard to find, I stop at various stores when convenient). Also I keep a list of cheap cabins to stay in with links to their websites.