Originally published in December, 2008.

It's every party host's nightmare (second only to a guest spilling a glass of red wine on the new white couch): running out of alcohol.

Pop and food are easy to replenish, but in most parts of this country, once the clock strikes 9, the liquor store is closed.

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So do the number-crunching beforehand. The general rule is one drink per person per hour. If this seems like too little, remember that most people drink less as the night goes on. Of course, having the right mix of booze is almost as crucial as having enough of it.

"The tendency for most people is to have one or two cocktails and then go on to wine," says Dinah Koo, one of Toronto's favourite caterers and co-author of The Cocktail Chef: Entertaining in Style.

Koo is a big believer in the signature drink, a special cocktail offered to guests at the beginning of the evening. (She shares recipes for several, along with dozens of yummy finger foods, in The Cocktail Chef.)

"I think it's really important," Koo says. "At Christmas time especially, something like the Cosmo is festive and sets the mood and the tone of the party." It's easy too. "Just pour the mix into a pitcher and go. Then you don't have to make a martini for each person."

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What if, despite all planning efforts, the bar does start going dry partway through the night? If it's too late to run to the liquor store and you're not on friendly enough terms to borrow from your neighbours, Koo suggests you "go into your cupboard and mix up a big punch" to stretch out what's left.

Here is Koo's basic shopping list for a five-hour cocktail party with 40 guests (for 20, go with a little more than half the amounts). Keep your guest list in mind: If you've got a beer-loving crowd, for example, buy an extra case. See The Cocktail Chef for a more detailed list.

The Cocktail Chef: Entertaining in Style by Dinah Koo and Janice Poon (Douglas & McIntyre), $35, available at http://www.chapters.indigo.ca.