How can you judge a wine? Like any commodity your demands of it vary according to circumstance. A wine chosen for a picnic on a beach is unlikely to be in the same style as one picked for a sumptuous dinner. Different expectations require different solutions. What you can judge, however, is whether a wine is well-made and suitable for its purpose. In matters of taste the final arbiter can only be oneself; the final guide can only be one's own palate.

Over the years a traditional scale for evaluating wines has evolved - simple, practical and effective. First you check your glass for colour; the wine should be clear and brilliant. Young reds have tinges of purple, older reds will have tones of brick-red at the edge of the glass - the meniscus. Young whites are frequently light in colour, often tinged with green, maturing into more honeyed shades of gold. Award marks out of three.

The aroma or the bouquet is next to be judged. It should be pronounced, and fruitiness and grapiness should be present. The colder the wine, the less the bouquet will be, as the volatile elements in wine need warmth to escape into the atmosphere and hence noticeable to our sense of smell. Swirling the wine in the glass helps this process. Award marks out of seven.

Lastly judge the taste, the most important factor of all. Obviously it should please, but look for intensity of flavours, a balance between acidity, sugar, tannin, fruit and alcohol. These last should be in harmony, no one element dominating the others. Your tongue can differentiate four basic tastes; sweet at the front, salty and sour at the sides and bitter at the back. A well-made wine will have a lingering taste, lasting up to minute after swallowing. Award marks out of ten. These three parts of the tasting process give you a mark out of twenty.

In America the 100 point system is increasingly used, most famously by Robert Parker. His scoring affects market prices enormously, yet there are arguments against publishing such scores. For one it implies that all wines are vying for the same award, a perfect score, yet this is clearly a nonsense - a fruity little rose from Anjou is not in competition with a classic claret. Secondly it suggests that wines can be scored once and for all for their shelf life, as well as implying that there's a clear difference between an 87/100 and an 89/100.

There's no doubt all wines are in competition for your money, but some aim to please with simplicity, others with complexity and others by simple refreshment. There's no common factor between them that makes sense of numerical scores across the board. The best and most reliable way to rate a wine is subjectively; trust your palate.

Wine of the Week

Leyenda Cabernet Sauvignon 1999

A wine that really pleased my palate, as well as winning awards across Europe. It's the top of the range from Chilean winery Vina de Larose and it's made from vines 55 years old or more, resulting in low yields, but great intensity of flavours. Not a cheap wine, but very impressive.

Available selected Dunnes Stores, €30.72