Every week, Mark Oldman -- wine expert, acclaimed author and lead judge of the hit series The Winemakers -- shares with readers the basics of wine, while making it fun and practical. In the coming weeks, he'll tell you what to ask at a wine store, at what temperature to serve it and share his must-have wine tools.

Contrary to common conception, it isn’t easy being the “wine guy” in restaurants -- your tablemates assume you always have a divining rod to the best bottle. But what happens when you don't get a good bottle? Or when you get a spoiled one? How do you politely send it back without being a jerk?

It was with extreme caution last week that I was in this exact situation: I sent back a bottle of wine at a New York restaurant. Although the server didn’t know of my connection to wine, she had already generously offered me tastes of two other wines they had by the glass. I turned them down gently and instead went with another, a red that she swore by.

When she opened the bottle and poured me a taste, I smelled trouble. Wet cardboard, damp basement, aged wrestling shoes -- call it what you may, but these are telltale signs of a wine being spoiled, which is why you sample wine in restaurants in the first place. The problem, then, was that I was already two strikes down. Sending the wine back confrontationally would be to foul-out into certifiable jerk status.

“You know, I think there might be something wrong here,” I offered, noticing that both my friends and the guests at the table next to us had gone silent, watching the drama unfold. The server panicked and summoned the wine director.

She arrived at the table and asked what was wrong. I knew what I needed to do to avoid escalating an already embarrassing situation: Bring her into the process.

“I think this wine may be off. Would you mind tasting it and seeing what you think?” With half the room now rapt, she took a taste and her reaction was immediate. She whisked the glass away with the efficiency of a Four Seasons bellhop -- no more questions asked. When she brought a replacement bottle to the table, the new wine was completely different than the first, with more flavor and no trace of that musty odor.

What this anecdote reveals is that it is never easy to send a bottle back, even for someone like me who writes wine books. Although experts estimate that at least 5 percent of all cork-closed bottles suffer from cork taint, that down-in the-basement moldy smell -- the characteristic sign of a wine being “corked” due to a contaminated cork -- isn’t always easy to call. Not only must you contend with the performance anxiety of judging a wine on the fly in front of your waiter and friends, but sometimes a spoiled wine smells only partially moldy. This is why the easiest way to send back a bottle is to bring your server into the fold and ask his or her opinion, assuming he or she seems fair-minded and helpful.