The big thing is hydrating the day before the race. I will have 20 ounces of water right when I get up in the morning the day before and I'll drink throughout the day.
I am fussy about my diet and straining my voice. I know sounds a bit over the top. But I'm not as bad as I used to be. These days I don't drink alcohol for five days before a show - very dehydrating for the vocal cords and all that acid reflux. I used to ban it for a fortnight. Nightmare.