(reveal your inner cork dork)
There are two main ways to taste wine: the fun way, and the technical way.
The Fun Way
1. Fill your glass.
2. Take a sip.
3. Think: "Damn, that's tasty."
4. Swallow and repeat.
The Technical Way
The point of doing this is to learn a little more about the wine as well as a little more about your palate. Doing this regularly will help you recognize flavors in wines more easily. It will also help you figure out what it is you like and don't like in a wine so that you can avoid wasting your money on the wrongs ones for you.
1. Look at the wine in the glass. You do this to assess visual flaws, and to get a guess at how old it is (of course if you aren't tasting blind, you should already know this). It helps to have good light and something white to hold your glass against. Generally, younger wines are lighter and brighter (white wines are lemon yellowish; red wines have lots of purple and ruby) and older wines are darker (white wines have more of a gold/amber/brown tint; red wines turn garnet/brick/maroon/amber).
2. Swirl the wine a bit and look at it again. Watch for the formation of legs on the glass. This supposedly gives you an idea of the alcohol or sugar content - higher alcohol and sugar leads to larger and faster moving legs. Legs are somewhat irrelevant though, as the type of glassware, atmospheric pressure, cleanliness of the glass and type of detergent used for the cleaning can drastically affect the formation of legs.
3. Give the wine a more vigorous swirl. This allows the wine to combine with oxygen and intensifies the aromas. This is rather important for enjoying your wine, as smell and taste work together. While the human tongue can only distinguish between five distinct tastes (sweet, sour, bitter, salty and umami), the nose can pick up thousands of different odors in minute quantities.
4. Stick your nose down into the glass and inhale deeply (but make sure your nose isn't actually in the wine when you do this...).
5. Think for a moment about what you're smelling, then try to isolate particular things you recognize: cherry, lemon, leather, blackberry, cotton candy, bacon. You can go back for another whiff to get some more, but your smell receptors do get tired quickly. By smelling the same thing multiple times you actually become temporarily numb to it (just think about the last time you were on a farm - it smells much worse when you arrive than when you leave). You can counter this somewhat by taking a sniff of something else, like the back of your hand, and then going back to the wine.
6. Take a small sip of the wine and hold it in your mouth. Aspirate it a little, bringing air into your mouth but being careful not to inhale any wine. This mixes the wine with more oxygen and releases aroma compounds that work with your taste buds to allow you to taste much more.
7. If you're tasting many wines, the next step is to spit out the wine. If you're just having a responsible adult beverage, then go ahead and swallow.
8. Compare what you just tasted to things that you've tasted in the past. Start with easier things you eat frequently - apples, strawberries, chocolate - then focus on the things you can taste but don't recognize. With some practice (or by tasting with a group and saying things out loud), you will be able to recognize many more flavors. Remember that smells and flavors can be very personal since they are linked quite strongly to memory. You may not smell the same things as a person with whom you are tasting.
10a. If you're tasting the wine with a bunch of people who know a lot (or act like they know a lot), then throw out some pompous phrases like "this is redolent of the wild lavender that grows in the eastern field of my home in the South of France". But say it with a straight face. This always throws people off, and they'll start looking for the things you mention. If you act like you know what you're doing, you'll be surprised to see how many people start agreeing with you.
10b. If you're tasting by yourself or with a group of friends that actually enjoy wine for what it is, then it's more useful to just be truthful. If something tastes like a clear Gummi Bear, then say it. Somebody else might identify this as candied pineapple, but that doesn't mean the other person is any more or less correct. Just spitball, throw ideas out, and only agree if you can actually taste or smell it. I love tasting with a group, recognizing a smell or taste but not being able to identify it, then hearing somebody else shout it out.