I have a notepad just for that. If a game doesn't have a quest log, then I need to write down NPC interactions and quotes. I still fucked up half of the quests, if not more, in Elden Ring. I also reference guides online for missables or certain items and make notes for missables and certain weapons and gear I would want, but try not to do too much spoiling. Also, lists of crafting items I need and in some cases, calculations and working out puzzles like the math codes in Stellar Blade.
Last list I had was a recommended order of progression through Demon's Souls.