Although less important than tasting and smelling, looking can tell you quite a lot about a wine.
Look at the wine against a plain white background:
Check that the wine is clear (no haze or murkiness) and bright. (If it looks dull it may well taste dull, too.) The finest wines often have a noticeable brilliance and lustre to them.
• Depth Of Colour
Look at the degree of colour — is it pale or dark gold? Ruby red, light pink, or brown? A deeply coloured, almost opaque red wine indicates high quality.
• Carbon-Dioxide Bubbles
CO2 is naturally present in all wines as a by-product of fermentation, but in most non-sparkling wines it is at a level which can be neither seen nor tasted. However, a few bubbles are sometimes visible at the edge of young white wines. In this case the winemaker has deliberately retained a little more of the wine's natural CO2 in order to enhance its freshness.
• The Colour Rim
The next stage is to examine the colour of the wine in detail. This gives some idea of the wine's maturity: the more brown or brick-hued it is at its rim, the older and/or readier it is to drink.
• White Wines
White Wines gain colour as they age, moving from the pale yellow of youth, through straw, dark yellow, various shades of gold and finally deepening to amber.
• Red Wines
Red Wines lose "redness" as they age, and the rim becomes almost clear. When young they are often bright purple; as time goes by they progress through red, ruby and browny-red hues to the almost mahogany tints of old age.
Swirl the wine in the glass, then hold it up to the light.
Some of it will cling to the sides before forming transparent "tears" or "legs". The richer and more alcoholic the wine the more evident these will be. They can hint at a wine's weight and richness, but they are a crude indicator and no substitute for what your palate tells you. At first you may spill the wine, but the knack is soon acquired.