Block the door open!
The reason is the cold refrigerator and freezer will tend to collect water inside.
It has to do with relative humidity - air holds water. Warm air can hold more water... when that warm air gets inside the fridge (when you open the door), it cools and can no longer hold the water that is in it. This causes condensation within the fridge. The condensation occurs anywhere air can get to, which is many places you can't see, like the backsides of all those panels.
When you unplug a fridge, it warms. That water evaporates, humidity goes to 100% inside, and it becomes a mold and mildew factory. Open it up 3 days later and the entire inside will be horribly splotched with mold - and it will be on the backsides too. It's impossible to clean it without taking the fridge all apart, and you can't get it all.
We had a genius "watt miser" who went around the lodge unplugging unused fridges. He did this no less than 3 times and wrecked the interior the fridge in every case. That's why we have a procedure now.
Now if you can block the door open, air will circulate in and out of the fridge, preventing 100% humidity from happening inside the fridge. People say you can close it after a few days, it's up to you whether to chance that. I use something (possibly taped in place) to force it to stay open 1/2" or so.