Before you taste make sure there are no distracting odors in the room, like cooking smells or perfume. The only thing you should smell is the wine in your glass.
Glasses should be clean and dry and filled with only a small sample of wine (about a quarter of the glass). Wines all have certain components and characteristics in common. When we taste, we use sight, smell and taste to recognize the various components and to assess the quality and health of the wine. So let's give it a go.

Sight or "Appearance"

• A good look at the wine can tell us about the condition and even age of the wine.
• Clarity: is the wine clear and bright (as it should be) or is it hazy or murky?
• Intensity: is the color pale or deep?
• Color: hold the glass at an angle against a white background (table cloth or sheet of paper) and assess the color in the middle of the bowl of the glass and at the rim. White wines start life pale and darken with age. Red wines start out a deep, bright purple and gradually turn ruby, mahogany and eventually brown as they age.

Smell or "Nose"

• Swirling the wine in the glass allows its aromas to be liberated into the air, so give your glass a whirl and then take a deep sniff. What are you looking for?
• Condition: does it smell clean and attractive or is there any mustiness or off-odor?
• Intensity: is the nose faint or pronounced?
• Character: what does it smell like? This may seem difficult initially, but you can do it. Just as you can tell the difference between the smell of bacon and coffee, you can also identify some of the possible smells in wine. Here are some things you may smell: fruit, grapes, lemon, grass, peaches, raspberries, blackcurrants, flowers, apples,  vanilla, oak, smoke, plums and many, many more. Remember that there are no right or wrong answers, here. It's simply an exercise in thinking about what you're drinking.

Taste or "Palate"

• Now the fun part -- you actually get to drink the stuff! Take a sip of wine and swirl it around the mouth so that the wine is in contact with all parts of your mouth: tongue, gums, soft palate. Even better, tilt the head forward so that the wine is behind the front teeth and then slurp air into the mouth over the wine. This seems weird at first, and goes against everything your mother taught you to do at the table, but it's worth it. You can taste much more of the wine if you aerate it in this way.

So what are you looking for?

• Sweetness: an easy one. Sweetness is immediately noticeable on the tip of the tongue. If there's no apparent sugar the wine is called "dry".
• Acidity: very important if the wine is to be refreshing and balanced. Lemon juice and vinegar are acidic. Too much and the wine tastes too tart; too little and the wine is known as "flabby", tasting heavy and just not refreshing.
• Alcohol: a vital component in wine, but one that shouldn't stand apart from the other elements if the wine is to be balanced. When the alcohol is too high, there will be a bit of a burning sensation after the wine is swallowed.
• Tannin: a natural preservative found in grape skins and stalks, tannin is the stuff that makes young red wines seem harsh and leaves the mouth feeling dry. If you want to know how tannin feels when it's not in wine, brew some very strong black tea and you'll soon know! Tannin's role as preservative is extremely important in high quality red wines that are made to age for many years.
• Body: an indicator of how the wine feels in the mouth. Pinot Noir or Beaujolais tend to feel quite light in the mouth while Bordeaux or Australian Shiraz tend to be full and dense. So, the progression for both reds and whites is light-bodied, to medium bodied, to full-bodied.
• Fruit: the taste and intensity of the fruit in the mouth; generally, the better the wine, the more evident the fruit. Also, younger wines will often display more fruit than mature wine.
• Length: how long the taste of the wine lingers in the mouth after swallowing is a good indication of the wine's quality: the longer the better.

Conclusions

Having considered the above elements, what did you think of the wine?

• Quality: you might think it's obvious to say that a $100 bottle of wine is likely to be high quality and a $5 wine low quality, but the assessment of quality goes beyond this. A wine that looks clear and bright, has a pronounced, intense nose, shows good fruit and balanced acid, sweetness and alcohol, and has a long finish might be an inexpensive wine. It would be classified as good quality, though, because it is a good example of its type. So as your tasting progresses, question the wine. Is it a good example of its type?
• Maturity: this is a measure of the wine's readiness to drink, which is not the same thing as its age. Many wines are made to be drunk as soon as they are bottled while others require years (or decades) of maturation in bottle to reach their optimum state. Simple wines, which are designed to be drunk young, will not improve with age. Rather they will deteriorate and be over the hill if kept too long.
• Faults: Thankfully, modern winemaking practices have reduced most of the problems we used to commonly find in wine, but there's still one which affects around a small percent of bottles: bad corks. "Corked", the term used to describe the affliction, has nothing to do with cork floating in the wine, but rather (not to get too technical) a condition in which the wine has reacted with a substance in the cork, producing a musty, corky smell and taste, reminiscent of wet cardboard. The wine should always smell clean and appealing. The cork problem is the reason behind many wineries switching to synthetic closures or screw caps, which are now widely used with aromatic varietals like Sauvignon Blanc and Riesling. So don't be put off is you see a screw cap on your wine. It doesn't mean cheap wine, it means the winemaker is sick of cork problems and wants to preserve the freshness of the wine.