The best thing one can do to enhance tea-tasting ability is to take notes on the flavor, mark how the tea was brewed, and ultimately to try as many different teas as you can.

How to taste
First, observe the dry leaf carefully. Does it appear to be broken or whole leaf, twisted or flat, regular or uneven? Smell the aroma of the tea leaves both before you brew as well as afterward. Note the color of the liquor in a white cup - is it green, yellow, gold, red or nearly black?

Next, taste the tea. To get the fullest flavor, we recommend you slurp it, taking the liquid into your mouth so that it spreads evenly over the entire surface of your tongue and reaches all of your taste buds at once. Don't be afraid to make a loud noise.

Flavor characteristics of the three major growing regions and types
Teas from a single country can exhibit a wide variety of flavors, but some basic generalizations can be made:
India and Sri Lanka Black teas are known for their brisk and pungent flavors. They are relatively lively and astringent, and usually take milk well. Some teas from these countries exhibit malty flavors, while others are citrusy and floral.
China Black teas are typically sweet, smooth, and slightly smoky. In some the smoky or toasty note is a subtle aromatic hint, in others it is strongly assertive.
Oolong teas are mild, fruity, and sweet. Oolongs are the mildest in flavor, yet can be quite complex, and yield a golden colored cup in between black and green teas. Oolongs come from China and Taiwan.
China Green teas are typically vegetal and light-bodied, with flavors ranging from nutty to earthy to floral. They are distinguished by their golden-green liquor and unique leaf styles.
Japan Green teas are fresh and vegetal tasting, with notes of newly cut grass and a hint of the sea. They typically have a bright green color.
Scented teas are brought into contact with a scenting agent such as jasmine flowers or pine smoke, and the aroma is transferred onto the tea.
Herbal "teas" are not truly tea, but are made up of botanical herbs, flowers, or spices. Herbal teas are also known as "tisanes."