Here are the four steps to properly tasting a glass of wine.

Look at the Wine
Pour a smallish amount of wine into a glass, (fill it about a third), and then hold it up to a light. Some people hold the glass up to a white napkin or piece of paper. Examine the depth of color. If you’re tasting a red wine you’ll look for anything from a fairly bright plummy red to a deep purple. The deeper the color the more full and intense is the wine. This holds true for whites as well. Some will be a delicate blonde color and others a darker color, like straw.

Nose the Wine
The scent or bouquet of the wine is a most important step in understanding its character, the terroir, and its intensity.  Place your nose inside the rim of the glass then close your eyes and inhale.  What aromas do you detect? Do you smell Coffee? Raspberries? Liquorice? Smoke? Spices? Chocolate? If you just smell wine don’t worry, your nose and your senses will soon be trained to detect these subtleties, it just takes a little time.  

       Swirl and Nose

The reason for only filling your glass to a third in step on is so that you can perform step three which is to swirl it.  Swirling the wine in a glass helps to oxygenate it and this releases esters which are an important component in the full taste of the wine.  The way the experts do it is to nose the wine, then swirl, then nose again. You will probably notice some delicate changes in the way a wine will taste and even the bouquet. You should also hold the wine by the stem or base so that the heat of your hand does not warm the wine in the bowl altering its flavor.  One important note, unless you are a professional taster or wine producer and want to assess the wine, it is best advised not to swirl your champagne or sparkler. Swirling these delicate wines will alter or destroy the elusive bubbles.
 But if you're not a fan of bubbles, swirling may be OK.

4.   4.    Sip the Wine
now is the moment when you get to taste. Take a small amount of wine in your mouth and roll it around or swish it for a few seconds. If you like you can suck in a bit of air at the same time.  The wine should linger on your tongue and now you’ll taste all the delicious things that you were able to smell when you were ‘way back in step 2.  You should be able to determine at this point whether you like this wine.  Professional wine taster s would then proceed to spit out the wine at this point, and you may choose to do so, but sometimes that’s a waste if you’re not trying too many and you just may want to savor it.