Now this isn't just pretense, nor just a way to avoid getting drunk. If you swallow, after a few tastes (and well before you're drunk) the alcohol in your system starts to contaminate your nose and your taste buds (think about it, breathalyzers work). This ends up masking a lot of the flavors and smells of the wine (a common complaint about high-alcohol wines in the first place).
That's all I'm going to say on that subject. I'm not so serious about tasting that I'm going to spend a day spitting wine into buckets, although I may not finish every pour even with wines I like.
Beyond that, what's the best way to taste?
The wine should be the right temperature.
White wines should be chilled. We're not talking ice-cold or even refrigerator temperature, just chilled. Say 50° give or take 5. White wines tend to balance out better when they're chilled, but beyond that the flavors just die.
Red wines should be "cellar temperature." That's not room temperature, particularly in summer. We're talking a just a little chilled, 60° give or take 5. Same deal as above.
That's not to say you can't drink red or white warmer, and many still hold up very well at room temperature.
So you've got the temperature right. Then there's the glass. Riedel Crystal has made a fortune convincing people that they need specific glasses for specific wines. Now this isn't total bullshit, but a basic wine glass is all you really need. A wine glass is designed to be filled part way; the inward curve towards the lip serves to capture the vapors coming off the wine. The stem (and yes, you can hold it by the stem, holding the foot is pure silliness) keeps your hands from warming the wine in the bowl.
Open the bottle and check the cork (if you're at a winery the hosts have already done this, tasted, and pitched any bad bottles). It should be springy and moist at the bottom. If it's mushy or dry, your wine is probably going to be nasty. Dry usually means oxidation in the bottle. Mushy probably means fungus, mold or mildew in the cork.
Pour in about an ounce. Take a look at the wine and consider the clarity and color. Hold it up to the light if it's a really dark red. Cloudiness and off colors are a sign there's probably something wrong.
Swirl the wine around in the glass. This isn't just pretentious bullshit. Swirling the wine encourages it to evaporate a bit, filling the rest of the glass with vapors. It also aerates the wine, helping along an oxidation process that will over the short term usually make the wine better (and over the long term destroy it).
If you look at the wine as it sticks to and runs back down the sides of the glass, you may see "legs" or "tears" forming. It's a pretty effect, but mostly meaningless. It's just in the nature of a liquid combining water and alcohol. Attributing any more significance to legs is bullshit.
Give the wine a healthy sniff, and consider the combination of smells from glass. Snobby folks will call this "bouquet" and less-snobby folks will call this the "nose." You're looking for pleasant smells such as fruit and alcohol, but you're also watching out for bad smells like mold and mildew. If the nose is unpleasant, the bottle is probably trash, do not pass go, do not collect $200.
Finally it's time to actually taste the wine. Put a bit in your mouth and slosh it around a bit. Again, not pretense but practicality. It's not just your tongue and a few taste buds that really make up taste; moving the wine around in your mouth gives you more of a taste.
Assuming that you haven't been chalking up warning signs and have to spit it out because it's disgusting (and that happens even in the best of wines; cork isn't perfect and storage sometimes goes wrong), think about what the flavors in the wine compare with.
"Body" describes how rich or thin the flavors are. Do the flavors linger and fill your mouth, or do they fade away quickly? Either can be desirable, or can be awful.
Flavors and smells start out pretty basic. There's fruit. What kind of fruit? Depends on the wine. Very rarely is it grape, though; "grapey" is generally an insult. Apple, pear, cherry, raspberry and others are common fruit flavors depending on the wine.
There's butter and vanilla. Buttery flavor comes from a particular fermentation process. Vanilla comes from aging in new oak barrels (pulling the sugars out of the wood). Both flavors are common in California Chardonnay; it's the style many winemakers have embraced.
There's alcohol. Too little and it doesn't taste like wine. Too much and it wipes out the other flavors.
Then the weird tastes start coming in.
"Tannins" are the flavors (acids, actually) that make your mouth feel a bit fuzzy and dried out. They come out of the grape skins when making red wine. Some red wines will display this effect more than others.
Mineral flavors (go lick a small piece of granite, you'll understand) are considered desirable, and actually do help other flavors balance.
Peppery (as in black pepper) flavors are common in some red wines.
Grassy and smoky flavors can come from barrel-aging. They're often interesting in small degrees but nasty if overdone.
Vegetable flavors (such as green bell pepper) can be desirable if they're well balanced, but often are way too strong. Under-ripe cabernet sauvignon grapes produce a very "green" flavor in wine.
If you're reading wine reviews to figure out what to buy, don't look too hard at the numbers. Figure out what you like about the wine you like, and what you don't like about the wine you don't like. Look at the review description of the tastes in the wine, and compare that description to your experiences. If it's not close, forget that reviewer and find one whose tastes are closer to yours. Choose new wines on the merits of the descriptions, not just the numbers.
If you just want to drink some wine, drink what you like. Taste when you have the chance to find out if there's new wines you might also like. Just don't get too wrapped up in the insanity.