When purchasing new wine glasses, consider the type you will be serving. Red wines require a wide bowl to let in more air and release all of the aromas and flavors while whites have more delicate flavors that require a narrower glass. You may even be looking specifically for a champagne glass or sweet wine glass. Whichever type of wine you will be serving be sure to consider the visual appeal of the glass too.
Crystal is the preferred material for wine glasses because it is very clear and thin. Crystal actually has a rougher surface and many wine connoisseurs believe that this surface allows wines to breathe better and open up more flavor nuances. It also has superior light refraction compared to plain glass. This enhances the colors of different varietals of wine, allowing the wine drinker to see non-distorted coloration of wine. Clear glasses for wine are also preferred for color evaluation purposes.
The thickness of the glass will also affect the taste. Taste depends greatly upon where the wine touches the tongue, and thin glasses, combined with the shape, direct the wine to the appropriate area of the tongue for the best taste. Thicker glasses send the wine to the wrong part of the tongue, which throws off the taste. However, thinner wine glasses are easier to break, so you will need to balance durability with functionality to suit your specific needs.
One final consideration is whether or not the glasses have a stem. Most wine lovers will tell you to go with a stemmed glass because it keeps your hands from warming the wine up; wine is meant to be served at cooler than body temperature. However, stemless glasses are a growing trend, and many people do not expect to hold the wine glass long enough to warm up the wine.