If making in advance, store the meringue in an airtight container, without any fillings or fruit. However, I wouldn't recommend making the meringue more than 1 day ahead. This kind of dessert has to be served and eaten the day it's made, for best results and taste. For leftover Pavlova, store it in the fridge because of the dairy toppings. The fridge will likely cause weeping of the sugar and the shell will become soggier as the toppings sit on it, but at least it will be safe to eat. :)