First and foremost, you need to make sure you are accurately measuring the spot where you plan on placing the fridge. You need to take into consideration not only the height, width and depth but the door opening radius as well. Having the mini fridge fit snugly, but not so much that the door can't be opened is the goal here.
And finally, you need to know just how cold your mini fridge needs to get. Some uses for a mini fridge require it to be only cool, and not chillingly cold. Other uses such as for sodas and beer, the colder it can get the better. Keep in mind that the more powerful a refrigerator is the more it's going to cost, but that's to be expected. Whether you require extra area for keeping foods at home, or need to have chilly beverages anywhere you're going, a portable mini fridge is right for you.