Nothing big, but I like to make colored cards with NPCs, treasure, mobs/minibosses, and small quests. Sometimes you just need a random mob, so shuffle the mob deck and draw one, if it doesn’t match the situation, draw another.
Regarding tabletop, we started with P&P and used erasing rubbers and such as figures and a square notepad as battle map.
Nowadays we have proper painted figures and nice battle maps, but sometimes we don’t even bring all that up for small battles, as we just do them verbally instead of visually.