Diners who ask for a restaurant's wine list tend to fall into two groups: those who know what they're after and will be disappointed if they don't find it, and those who accept the carte des vins  gingerly, as though it might ignite in their hands. If you're in the latter camp, your aim is probably just to find a tasty, affordable bottle to enhance your meal. Here are some basic principles that will increase your odds of achieving your objective without losing your shirt. 

AVOID THE CHEAPEST AND THE MOST EXPENSIVE WINES: Most restaurants calculate a minimum price for simply handling a bottle: for storing it, for rooting around in the bin to find it, for opening and for serving it--one hopes at the proper temperature and in suitable glassware. In a low-end eatery, this overhead cost may be as little as $5, while in a ritzier spot it may be $15 or $20. Markups tend to be figured on a sliding scale: higher for inexpensive items, and lower for pricier wines. A wine listed for $20 may have been purchased wholesale for $4, while one selling for $45 might have cost the restaurant $18. As a general rule, you don't want the $4 bottle, especially if it has been marked up 500%. At the top end, wine-savvy diners can often find relative bargains, although many restaurants apply breathtaking markups to the most widely prized prestige wines and scarce items. If you don't know roughly what these wines should cost, proceed with extreme caution. 

LOOK FOR OFF-THE-BEATEN-TRACK AREAS THAT ARE WELL-REPRESENTED: Most wine lists in America are heavy on California, France's snob areas like Bordeaux and Burgundy, and the more famous wines of Italy (Chianti, Barolo and the like). If your carte des vins offers multiple selections from a region such as Alsace, the Loire Valley, South Africa or Washington State, chances are that there is someone on the premises who genuinely appreciates these wines and would like you to enjoy them as well. Their prominent position on the wine list is a message that the restaurant managers feel these wines go well with the house cuisine. 

DON'T GET HUNG UP ON VINTAGE CHARTS: Most vintage charts give only a rudimentary overview of how a broadly defined region performed in a given year. The producer's name on the label is easily as important an indicator of quality as the vintage or the specific vineyard the wine is from. The most talented growers and winemakers manage to make very good wine in average years, while underachievers will make mediocre juice even under ideal conditions. On the other hand, if you're in a restaurant that lists its wines without showing their vintage, it's a good bet that the management is heedlessly buying the same uninspiring items year after year. In this case, I'd recommend finding out the year and then consulting your vintage chart--to know which years to avoid.