Select your tipple for the evening. Pour about 50mls into a wine glass.
Hold the glass at a 45 degree angle, ideally in a well lit environment and against a white background (you can use some white paper or a wall, for example).
We're looking for colour and clarity.
Commercial wines generally have good clarity - when you look at them you should be observing that they are clear, brilliant, or transparent. Some wines though will have poor clarity and these might be described as dull, cloudy, or hazy. Most winemakers will rack wine to remove sediment that can cause cloudiness, or use a clumping agent to help remove remaining yeast. Clarity is taken as an indicatory of quality - and although cloudy or hazy wine won't always impact taste, it often indicates the care with which the wine was made.
Colour can be described in terms of depth and hue. The depth, or intensity, of a wine can range from pale and light through medium to dark or deep. Hue refers to the shade of colour. White wines are typically pale when young and can show a green tinge (from residual chlorophyll from the grapes), and will be darker yellow as they age. Reds move from crimsons when young through to brick reds and even browns when old.