They say the one look at the label is worth 30 years blind tasting. That's because the label will tell you the vintage, the alcohol level, the region the wine comes from, its classification (for example, AC or Vin de Pays) and the name and address of the producer. National and international laws set out basic levels of information that labels must convey, but in addition lots of wines have back labels which tell you when to drink the wine, how sweet it is and what sort of food it will go with.

Wine bottles have corks to exclude the air. Screw caps will do the job as efficiently, but they don't look as nice, and the fact is, we all like playing around with corkscrews. But good-quality corks are expensive, and producers are increasingly using synthetic corks for inexpensive wines. They're sometimes brightly coloured, so we know nobody's trying to fool us. My corkscrew still works on them, so I'm happy. The one I'm using here is a Screwpull, which is smoothly efficient and seems foolproof; the Waiter's Friend and other level models are also easy. But any corkscrew with and open helix will do the job efficiently. A solid helix is more likely to rip through corks, especially old and fragile ones.

The colour and depth will tell you a good deal about whether it comes from a cool country or a hot one (hot country wines have a deeper colour, on the whole), a frail grape or a gutsy one (again, frailer grapes tend to have paler colours), and the wine. Tilt the glass against a white background, preferably in daylight and definitely not under neon light. That way you can see the range of colours of the wine, plus any lighter rim that comes with age. Sometimes the colour is so beautiful it's worth gazing at for a while to heighten your expectations.

The first thing to do is to pick out any toughness or acidity, which you will feel in your mouth, and then experience all the personality and flavour, which you will 'taste' in your nasal cavity - breathing out carries the aromas to your nasal cavity. Now, quite literally, chew the wine - as if you had a piece of meat between your molars. And concentrate. You want to clock, first you spontaneous impressions, then the actual taste that will develop after the wine has been in your mouth a few seconds, and finally - after you've swallowed or spat out the wine, which in turn depends on whether you're doing this for fun or work - the persistent, lingering taste which wine-tasters call the 'length' of the wine. The flavours may blast you unchagingly from the first whiff, or they may shift as tantalizingly as sand under the rising tide. In either case, do make notes as you go. It's incredibly difficult to remember a flavour, five or six wines later.

Basically, what you're trying to do is assess the wine's quality, and its probable development. There are four basic pints to look for. First, acidity. Any wine, be it sweet, medium or dry, must have acidity to be refreshing, and to be able to age. But one acid you don't ever want is acetic. That's vinegar. Next, tannin. This comes from the skins and pips of grapes, and is found in red wine: it's the rasping, tooth-furring component that dries your mouth out. It's necessary in greater or lesser amounts if a wine is to age, but it must be in balance with the fruit. The fruit is the next thing to look for - wine is made of fruit and without it wine is no fun. Then there's colour. Lots of colour is not always necessary. Some reds. Like those from Pinot Noir, rarely have a deep colour, but may still be full of flavour. Some good whites, especially Rieslings and Sauvignons, have almost no colour at all.

Why spit? Well, there are plenty of occasions when spitting would be highly inappropriate: most social situations, for example. But if you've set up a serious tasting with like-minded friends, or you're tasting in a grower's cellar on holiday, then spitting is the order of the day. It's the only way to taste a lot of wines and stay sober. It helps to keep your palate clearer for longer, too. You don't need a special spittoon: a bucket will do. Sawdust in the bottom will make it look less unpleasant. And put newspaper underneath it for those with poor aim.

If the flavour ligers in your mouth after you've swallowed or spat out the wine, then that's a sign of quality. And the longer it lingers the better. If the flavour falls away rather quickly - well, don't' reckon on laying that wine down for too long. But it isn't just tough, dense wines that can age well. Sometimes a pleasant, approachable, fruity wine just goes on and on - that's quality without tears.

High wine-making standards in most countries means that faults in wine are rarer than they were. The commonest fault is oxidation, which usually shows as a staleness, a flatness, on the nose and palate. It means the wine has been exposed to too much oxygen. A little is necessary for wine to mature; too much leads to oxidation. Corked wine is recognizable by its mouldy, stale smell - it's caused by a chlorine infection in the cork - and the smell is unmistakable once you've suffered it. Dirty tastes in wine can also be caused by dirty barrels. Too much sulphur (some sulphur is needed to prevent oxidation) smells like spent matches. If the wine fizzes when it shouldn't, and has a yeasty smell, then it may be refermenting. If it's hazy, it may have a chemical problem - but it it's a mature, fine wine you may just have shaken up the sediment. See what it tastes like.