I go for a nap. That is not always possible, but for a late night session it offers a nice edge plus makes the game more enjoyable.
Homegame: I nervously stack and re-stack the starting stacks. Count through the decks to be used. Fan the decks. Realize the fan isn't perfect, so recount the cards and re-fan. Restack the stating stacks. Adjust the card fan. Try to remember if I actually have cash to play in my own game. Add songs to playlist. Try to figure out which player will felt me. Restack starting stacks. Think about having a beer. Don't have a beer want to stay sharp. Definitely want to stay sharp. Focused. Have a beer. Restack starting stacks.
Casino: Think about how I can stretch my initial buy in to the 30 minute mark.
Interesting - - - - my problem on the Saturday game is early arrivals. Food is served nominally at 6:45 but someone is often there by 6:30 and rarely at 6:00. I don't remember ever staring that game late.
I have the same pre-game hosting restlessness which leads me to adjust lights, table, cards etc until about 1 min before guests are supposed to arrive. Then I spend the next 30 minutes sitting at the table aimlessly looking at my phone waiting for the first (late) guest to arrive, wondering why I started setting up so early. Every. Single. Time.