I make sure I have a big meal - take a nice hot shower. And get to bed early. I like to eat a lot of carbs and lean meats the night before. And then the day of - just eat light and drink a lot of fluids.
I also tend to do the pillow drill. Where I prop a pillow up against the wall - like a couch pillow - and hit forward press chip shots into it. Just to help educate my hands. I get to a distance where the ball will hit the pillow and roll back to me. So basically I can just stand there and hit dozens and dozens of shots over and over. And really work on feeling the clubhead making impact with the ball. And if I have enough time... I'll spend time rolling putts on my putting alley.
The short game is critical to scoring - and this is where I want to spend my 'crunch' time before a big event.