Many people are intimidated by wine tasting, and are not sure what to look for when presented with a glass. Wine tasting is in fact largely based on logic, and on experiencing what is presented to you.
The first thing to do is look at the wine in the glass. What does its colour look like? Look for murkiness, brightness and intensity of colour. Next, gently swirl the wine in the glass to expose it to oxygen. This exposure releases more aromas and helps the wine develop. By smelling the wine deeply, you will get a first glimpse of the complexity and layers of flavour. You should be able to identify distinct 'noses', such as floral, chocolate, smokiness, tabacco and so forth. The better and more complex the wine, the more noses you will be able to detect. Of course, not all aromas are good, and reduction, oxidation or a corked wine will be detectable in the wine's nose.
Now sip a little bit of wine and swirl it around in your mouth. By sucking in some air, you will liberate its perfume further. Let the wine reach your palate and feel the texture. Is it smooth, chalky, sticky or silky? After you swallow (or spit), the aftertaste will linger in your mouth. Try to assess the body, acidity and tannins in the wine, as well as the intensity of the flavour. Then, try to identify specific flavours. This can be anything from butterscotch to berries. The balance between these flavours is also important.