Just what is a sommelier and how do you use one? It’s important if you’re having dinner in an elegant restaurant with your boss, future in-laws or new squeeze you’re trying to impress.

It can be stressful if you let it.

So don’t let it.

First, it’s pronounced SAHM-el-yay. These days it’s often shortened to “somm,” and they’re seen more and more in upscale restaurants. It’s the person who shows up with the wine list after you’ve seen the menu. In a top restaurant, he or she should be well-educated about wine in general and wine-food pairings and thoroughly familiar with the restaurant’s menu and wine list.

An expensive meal should be fun, so here are a couple of tips:

If it’s a super-important occasion, go to the restaurant’s website beforehand and go over the menu and the wine list. Get some rough ideas of what you might like to have. But keep an open mind.

When you get there, treat it as an adventure, not a test of your personhood.

Don’t — oh don’t — try to fake it. It’s the surest way to look foolish. Don’t go mano-a-mano with the somm, who well may know more about wine than you do. In any case, his or her goal is to make your evening enjoyable, and being friendly and non-snooty is part of that duty.

Here are some sample conversations you might have with the somm:

If you don’t want to use the somm, just say, “I’d like to choose the wine myself, but thanks for offering.”

If you know little about wine: “I’m having the roast pork and she’s having the leg of lamb. We’re not wine experts, so what would you suggest?” Here it’s important to establish a price range. You can simply say, “Something in the $30 range.” Or, to be subtle, you can point to a couple of prices on the wine list and say, “Maybe something in this range.” The somm will take your hint.

If you know a little more out wine, tell the somm: “I tend to like light-bodied wines, not too powerful or alcoholic.” Or, “I like hearty, full-bodied red wines and super-oaky chardonnays.”

If you know a lot about wine: “I’m tempted to get the 2010 Shafer Cabernet Sauvignon. Or do you know something that might be even better?” You don’t have to follow his or her suggestion.

Or you might even say, “Surprise me. You’re the pro.” But be extra-sure in this case to make clear the price range.

If you’d like to know more about wine, turn it into a learning experience by tapping into the expertise of the somm. When you’ve tried the wine, say something like, “This is very nice. Tell me why you recommended it with the veal.”

When the somm brings the wine to the table and presents it to you, check the label for its name and vintage year very carefully. This could prevent a $300 misunderstanding. If it’s correct, simply nod.

Now the somm will open the wine, and possibly pour a tiny portion into a glass and taste it. Don’t be offended. He or she is simply making sure it’s not spoiled. It could spare you a nasty surprise.

If you don’t want him or her to do that, just say, “I’d rather test the wine myself.”

The somm then will place the cork on the table in front of you. Don’t pick it up and make a big deal over it. Simply glance at it. If it’s broken or soaked full-length with wine, it means the seal might have been broken and the wine might be spoiled. But you can’t be sure until you taste it, so don’t waste time over this step.

When the somm pours a tiny portion in your glass, simply take a quick sniff and sip. If it’s spoiled, say so and the somm will send it back. If it tastes like wine, simply nod your head. You don’t have to ooh and ahh over it. The somm didn’t make it.

Oh, and if you chose the wine, you can’t send it back if it’s sound, but you simply don’t like it. On the other hand, if the somm recommended it and you don’t like it and can articulate why, ask for a different wine. Some restaurants will allow this, others won’t.

Now the somm will go around the table pouring the wine — women first. Watch carefully. Wine glasses should be poured less than halfway full, to leave room so you can swirl it to release more of the aroma to enjoy. If the somm pours too much, quietly ask him or her to pour less.

(I was in a restaurant once in which the somm poured three glasses full to the rim, emptying the bottle before the fourth guest got any, and announcing: “I guess you need another bottle.” Imagine the size of his tip.)

If you want, tell the somm that you’d like to pour the wine yourself for the rest of the meal.

Now to that dreaded moment — the tip.

You usually don’t tip the somm separately. For the most part I simply tip about 20 percent of the entire bill, both food and wine. Or 15 percent of the service was subpar. Most restaurants have a policy of dividing the tips among the waiter, the somm and the rest of the serving staff.

Two exceptions:

If the somm has gone above and beyond, ferreting out the finest bottle or food-wine pairing of your life, you might quietly hand him or her an extra $5, $10 or $20. Along with your thanks.

If you’ve chosen a wine that cost more than the rest of the meal, you might tip 20 percent of the meal and less on the wine. It’s no more work to pop the cork on a $500 wine than on a $30 wine.

A final note: Wine fans don’t always agree on how to deal with somms. If any diner or somm disagrees with anything I’ve said, please email me at the address below so we can talk about it.

Fred Tasker has retired from The Miami Herald but is still writing about wine. He can be reached at fredtaskerwinegmail.com.