For a tasting, still wines should be served at between 16 and 18°C (60 and 64°F), even if the wines would usually be served chilled. At this temperature, the aromas and flavors of the wine are believed to be most easily detectable. It also ensures that the wines can be judged in a standardized way.
Serving of a wine cool can help to mask the flaws seen in young or cheap wines, whereas serving wine warmer can allow the boquet and complexity to be expressed, which ideal for aged and expensive wines. Lower temperatures also repress the 'bite' that alcohol can give in lighter bodied wines.
The exception to this convention is sparkling wine which is usually tasted chilled. The thinking behind this is that many sparkling wines can be unpleasant in the mouth when they are warm.
A good rule of thumb is the Rule of 20: place red wines in the refrigerator 20 minutes before serving, and remove whites from the refrigerator 20 minutes before serving. 

Order of tasting

Tasting order is very important, as heavy or sweet wines can dominate lighter wines and skew the taster's assessment of those wines. As such, wines should be tasted in the following order: sparkling wines; light whites, then heavy whites; roses; light reds; heavy reds; sweet wines.

Without having tasted the wines, however, one does not know if, for example, a white is heavy or light. Before tasting, try and determine the order the wines should be assessed in, by appearance and nose alone. Remember that heavy wines will be deeper in colour and generally more intense on the nose. Sweeter wines, being denser, will leave thick, viscous streaks (called legs) down the inside of the glass, when swirled.