A friend was up from Connecticut on the weekend. "Guess the latest restaurant wine trend in New York," she teased.

"Petrus by the glass?" I sarcastically ventured. "Wine bars selling only Austrian gruner veltliner?"

"Shut up," she said. "People are haggling."

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Apparently, Manhattan's newly frugal foodie class is running its collective pinkie across expensive wine lists and asking waiters, "Can you do any better on the price?" More surprising, sometimes the waiters are saying yes.

I've asked around in Canada but no establishments I know of are reporting incidents of this inspired New York-style chutzpah. It would be perfectly legal, though, in case you were wondering. In Ontario, for example, a restaurant can discount wine from the regular price as long as it doesn't fall below the threshold of $2 a glass (or roughly $10 a bottle), and there's no threat of that happening, clearly. But I'm happy to report that some resourceful Canadian drinkers are resorting to another strategy to keep a lid on beverage costs. They're taking advantage of bring-your-own-wine policies. Legal in at least four provinces (Alberta, Ontario, Quebec and New Brunswick), the policies enable patrons to bring in wine and have it served as though it had been purchased from the restaurant. In exchange, the place charges a "corkage" fee to cover service and glassware maintenance costs. Typically corkage runs between $10 and $40.

"We've certainly seen a spike in the number of people who bring their own," says Carl Korte, a partner at Scaramouche Restaurant in Toronto, which has been permitting the practice since it was legalized, on a voluntary basis, in Ontario in 2005. Mr. Korte says that in the first year his staff handled "maybe one or two bottles a night." But in the past few months, the volume has surged.

"It's not uncommon to get 10 bottles a night." His corkage fee is $30, typical for a high-end restaurant.

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It's not just individual patrons getting in on the savings. Organized groups such as office-party gatherings are BYOC-ing it - bringing their own cases - to private functions. "It used to be strange if a party requested to bring in their own wines," says Jenn Urban, the event co-ordinator at Saltlik restaurant in Calgary. "Now it's fairly common." The same is true at Calgary's Artisan Bistro, where the bring-your-own phenomenon is more popular with groups, such as small weddings, than with the regular restaurant crowd. Adds Valeria Lagos, a part owner, "but a lot of people still don't know they can do that."

In fact, I didn't know the policy applied to private-dining functions till I made a bunch of calls for this column. I got an earful from restaurateurs and learned a few other things, too. Permit me to offer a user's guide to BYO law and etiquette.

Banned in B.C. Most provinces, including British Columbia, do not permit patrons to carry their own wine to restaurants. Of the progressive four that do, Quebec and New Brunswick permit it only at restaurants that do not already have liquor licences. The only jurisdictions with licensed restaurants that also allow BYO are Alberta and Ontario.

Call ahead if possible. Make sure the place has a BYO policy. Most restaurants, even in Alberta and Ontario, don't. Just 1,509 of Ontario's 17,500 licensed establishments permit the practice. Although there's no cost to the restaurant, the owners must apply for a special BYO "endorsement" that ensures they don't have a record of liquor-laws violations, such as serving to minors.

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Drop it off in advance if you can. Restaurateurs will like you. This helps staff prepare the wine properly by chilling or decanting if necessary and avoids any kind of awkwardness as you arrive. Also, incidentally, it's a guarantee to them that you'll actually show for your reservation.

Don't force your bottle on the front-desk host or hostess. Some restaurants, including busy high-end establishments such as Scaramouche, prefer that you take your bottle straight to the table. "Tell the server how you'd like it dealt with," Mr. Korte says. "Everything flows from there. By involving the hostess, then you are creating another channel of communication and the waiter's not sure if he's supposed to offer cocktails." Not every restaurant is the same, so always ask before pushing your bottle into anyone's hand.

Believe it or not, you can take home leftovers. At most BYO restaurants, customers can keep what they don't polish off. It's all in the name of responsible consumption, designed to discourage overindulgence. There's a condition, though. The bottle has to be resealed, with the cork flush with the bottle top. Did you bring a screw-cap wine? If the restaurant can't find a spare cork to fit, it's either drink up (and call a cab) or kiss your leftovers goodbye.

No spirits, suds, sherry or port. Generally, BYO laws don't apply to hard liquor, beer or fortified wines. Leave the Bud Light and '27 Cockburn at home.

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Eschew the u-brew. Restaurants can only accept commercially made wine in a sealed bottle. That's the law. No South Calgary sangiovese or Cabbagetown cabernet. Besides, if you're going to be that cheap, why aren't you at home boiling Kraft Dinner?

Buy a glass from the restaurant if possible. You certainly don't have to, but if the night calls for an aperitif, consider springing for a cocktail or glass of prosecco from the list. It's a way to score points with your waiter, should that be a desired state of affairs. It also will convey that you're not a total skinflint should that for some reason be in question. Which brings me to.…

Tip generously. You need not do this either. But it's the decent thing and I'm assuming you're a generous sort. Bear in mind that BYO programs usually cut significantly into a restaurant's take, even after the corkage fee. Most restaurants operate on phyllo-thin margins. (If only I could publish restaurateurs' tales to me of wealthy gluttons who strut in with $500 trophy bottles and then tip like Henny Youngman. But too many of them happen to be litigators and I'd go bankrupt defending myself in court.) And speaking of skinflints.…

The big-bottle shuffle. Corkage fees apply to volume, specifically 750 millilitres, not to the largest container you can carry. Blair Aspinall, a partner at Zucca Trattoria on Yonge Street in Toronto, recalls a customer who tried to bicker over the $50 corkage he charged for a double-sized, 1.5-litre magnum. (Zucca's regular corkage is $25.) Mr. Aspinall might have cut the customer slack had the large-format bottle in question been a treasured old cellar gem or magnan- imous charity-auction purchase. Instead, it was Yellow Tail Shiraz. Ontario retail price for a magnum: $23.75.