If the cardinal rules of party planning do, in fact, exist, this one is at the top of the list: Always plan on ordering, preparing, or mixing for at least 1.5 times the number of guests. (For beverages, it should be 1.5 times the number of guests per hour.) Not exactly sure how many friends will be joining? As a general principle, always round up. That way, you’ll be covered for any last minute plus-ones or hungrier-than-expected guests. And if you don’t want all the leftovers, purchase some disposable to-go containers for visitors to fill up before they depart.