1. Inclement Weather

For an outdoor reception, pick a venue with a big enough, nice enough indoor space (book both at once, in one contract). Or, if it’s allowed, reserve a tent (be ready to put down a 50 percent deposit). Go to Plan B a week before your wedding if the chance of rain exceeds 60 percent. Don’t wait; tent setup can take up to three days. If you fear the worst—having to postpone—buy insurance early on ($195; wedsafe.com).

2. Late Arrivals

If your ceremony and reception sites are far apart, provide your guests with transportation to guarantee no one gets lost along the way or is stuck circling for a parking spot. Reserve buses (try Local Coach Lines). The day before the wedding, make sure the drivers have an accurate schedule and directions. On the day-of, notify drivers of any traffic advisories (check traffic website.

4. Drunken Behavior

Make sure that the first trays of hors d’oeuvre are passed not too long after “I do”—though sometimes unavoidable, a lull between the ceremony and reception basically guarantees pre-partying. For the cocktail hour, delegate a bridesmaid to keep the food coming and make sure the band starts on time. A musicless room may inspire tipsy guests to create their own entertainment.