I'm going to assume that you're comfortable talking to a sommelier, which is both admirable and a tad abnormal.
Most people who ask me questions about wine are terrified of talking to the somm for fear of broaching the "wrong" questions, revealing their inferior tastes, or, in general, sounding like a buffoon.
In the other extreme, of course, are the buffoons who love to talk to somms just to hear themselves pontificate about things that make them feel important (i.e. "I see you have the '82 Blahdeeblah; I have six cases of that in my cellar, but they're coming along rather slowly at present.") I'm hoping this doesn't describe you, of course.
So back to my advice.
First, and foremost, make sure you're actually talking to the sommelier or wine director. In other words, never, ever, ever, ever ask the waiter for wine advice. I'm not being a d--k here, but rather defining roles: Waiters serve food, should be able to discuss ingredients and preparation, and offer impeccable service. Period. Ask for a wine list. Look at the menu, figure out what you're going to eat, and then ask the waiter to send over the somm or wine director.
Next, reveal everything you're thinking: "Hi, I tend to like to drink Cabernets. My friend here prefers red Burgundies. I'm having Skate Wing in beurre blanc; he's having the pork chop smothered in mushrooms. We're thinking of spending $75 for a bottle of something you recommend. What do you think?" The point is to engage the somm, show interest, ask questions, let him do his thing. Trust me, you cannot imagine how many somms are bored to tears because nobody asks for them, or worse, treats them like waiters.
Finally, if the rapport feels good, the banter is genuine, and you think you could close the deal, ask the somm something like this, "If we put ourselves totally in your hands, trusting you to give us a bottle that you yourself love, is there one bottle on this list—or, even off the list—that you'd order without hesitation? We're totally willing to gamble with you."
I've often played the dumb fox with somms just to see how they react. I cannot tell you how many have risen to the occasion and made thoughtful recommendations. Sometimes—it doesn't happen all the time—they'll even go down into the cellar to bring up something they'd forgotten was down there, or was just taken down from the list. Ultimately, it all depends on how well you finesse it. It all begins with a conversation.