When shopping for beer, wine or liquor, opt for the big packages. In most cases, you'll pay less per ounce for a case of beer (and even less for a keg) than for a six- or 12-pack. Larger containers of spirits and wine are also less expensive per ounce. Boxed wines are the best bargain. If you don't like the idea of serving wine in boxes, put it in simple glass carafes for guests to help themselves, or use your slow cooker to make mulled wine.
Be prepared to pay cash for your libation supply: Most liquor stores give a discount for cash purchases, as well as if you buy wine by the case.