I'm going into my 3rd show, though I've prepped for 4 w/ 4 different trainers. There are a number of different approaches to the last week so I am not going to say "THIS" is the one. It all depends on the person, the shape they are in, etc. You have to go thru a dialing in process the last week that gets tweaked on a daily basis depending on your progress, your goal and each day's status.
I would suggest that before you go diving into competition, several weeks out, experiment with how your body reacts, for ex which carbs work best for you, how long do u take to fill out, etc.
Generally people will follow what I said above for that last week's schedule but I suggest you do a lot of your own research. There's some good articles on bodybuilding.com and also look through our own competition board.