If you're doing your own catering, you need to know how much alcohol to buy. Keep in mind that you'll need less for a morning reception than an evening one. Think of who your guests are. A more genteel crowd may be content with some good wine, but the groom's college buddies may prefer beer. When you factor in the guests who won't be drinking alcohol, the average consumption will be about one drink per hour. In general, count on two cases of beer, three cases of wine and a case and a half of champagne for 100 guests. Two fifths of the more popular liquors -- vodka, scotch, bourbon, whiskey and rum -- should be plenty. Don't forget to purchase mixers such as fruit juice, soda and water, too.