Most wine regions have some sort of classification system, and recognizing them will help you better understand wine labels. In the U.S., regions are divided into American Viticultural Areas (AVAs). In Italy, they are called DOCs. Wines labeled DOC, DOCG, and IGT are the most rigid classification systems, so they are usually high quality. When it comes to Spanish wines, look for wines labeled DOP, DOC and VT for the best quality.
In France, wines labeled AOP are the highest quality, while wines that say Vin de France (a lower classification) can be great value. It gets a bit more confusing when you look at Burgundy and Bordeaux because these two regions have their own quality systems. In Burgundy, premier cru and grand cru wines are at the top of the pyramid, whereas in Bordeaux wines are classified by growth, with first growth being the absolute most valued wines in the region. (If you're curious, you can expect to pay about $1,000 per bottle for those wines from a first-growth chateaux.)