The Wine Geek explains corkage fees, tips, and when it's OK to BYOW to a restaurant.
Q. When is it considered OK to bring your own wine to a restaurant?
A. Not all restaurants permit “BYO,” and many that do charge per-bottle corkage fees ranging from $10 to $50. Even when you pay the corkage fee, there are still a few breaches of etiquette that can peg the tacky-ometer to the limit. First, and worst, is to bring a wine the restaurant already carries or one that costs less than the corkage fee. The older, rarer or more expensive your bottle is, the more likely it is to be welcomed with open arms. Actually, if you’re celebrating a special occasion with such a wine, it is entirely appropriate to ask whether the restaurant might be willing to waive corkage fees. When restaurant staff is gracious about your brought-in bottle, the onus is on you to respond in kind. Be sure to offer the sommelier or waiter a taste of your special wine. And when corkage is waived, practice the most-appreciated form of courtesy: Add the price of your wine when figuring a tip.
—Charles Smothermon, a food and wine writer in Laurin, Mont.