Letting your turkey sit in a salty/vinegary bath for 24 hrs before roasting will help ensure you have a moist and flavorful turkey.
To brine your turkey, place it in a large vessel (like a stockpot) and cover completely with brine. Let sit in the fridge overnight.
The brine can be a simple solution of water, vinegar (flavored or plain), salt, and spices/herbs. Citrus is a great addition. Do not use olive oil in the brine.
Remove turkey from brine and let sit on a dry towel in the fridge for a few hours before roasting to give the brine a chance to drain.