The first thing I want to say about blind tasting is that it should be fun! Try to shake off the pretension, do not worry about what others will think of your guesses, and just enjoy the beverage. This will put you in a relaxed and casual mood, ready to enjoy the experience and get to the origins of your blind wine without pressure.
Next, you will want to remember to use your senses. Start with sight. Eye the wine. This will give valuable clues. The color and depth will vary between varietals, but know that those varietal characteristics normally remain constant. Sauvignon Blanc can be light straw while Chardonnay tends to be light golden. Pinot Noir is normally light red and translucent, while Cabernet Sauvignon will be darker red and opaque. Get to know the how each varietal looks and this will be a big clue toward picking correctly.
Use your sense of smell. This will tell you the difference between what is called an Old World wine and a New World wine. Old world wine are those coming from Europe, Eurasia, and the Mediterranean, while New World wines come from the Americas, South Africa, New Zealand, and Australia. Most of the difference comes from the soil, yeasts, and aging. The surviving Old World varietals have been growing in their soil since the Roman Empire or even before. They have dug into the richer portions and been extracting complex minerals. The smells they give off are more secondary (created through fermentation) and tertiary (created during aging). Secondary aromas are floral and fruity while tertiary can be barnyard, damp oak, wood spice, nuts, or caramel. New World wines are newer to the fresh soils and the wines give more primary (characteristics of the grape varietal) and secondary smells, though alot of new oak is used and can give rich spice. Get to know how each varietal is treated (particular yeasts and stainless steel or oak aging) and you will get closer to your conclusion.
Now for everyone's favorite: taste. Start by judging acidity. If the wine makes saliva build up in the back and sides of your mouth, it will have a higher acidity level. This will back up your climate findings from earlier. Judge the tannins. If you feel a sharp tug on your gums, the wine will have a higher tannin level. Varietals with thin skins, like Pinot Noir, will not have the rich tannins of a thicker skinned Cabernet Sauvignon. Judge the alcohol. If you feel the heat in your mouth and slight burn in your chest, you will know the wine has more alcohol. This will mean it was able to gain more sugar because it was grown in a warmer climate. Dry wines will normally have between 9-16% alcohol. Now try to figure out which primary, secondary, or tertiary flavors are coming through. If they come close to corresponding with your smells and has long flavor length, then it is a quality wine. Judge the body. Light has a similar feel to that of water, while heavy has the feel and weight of cream on the palate.
For age, tilt your glass and put it up to a white background. If the meniscus (edge) varies in color and has a bit of brown when compared to the rest of the wine, then it is older. Add this up with your smell conclusion (the wine will also give more tertiary the older it gets) to judge an age range.
An example of a conclusion would be: "I see a light straw color with no edge variation. I smell citrus and gooseberry. The wine has crisp acidity, low tannin, medium alcohol, medium body, and flavors of grapefruit. It is a 1-3 year old New Zealand Sauvignon Blanc."
Store each wine experience in your mind or in a journal. Try new varietals, viticultural areas, and countries. Memory is your biggest weapon in blind tasting.
Now that you are armed with this info, go out and get some tasting done! For practice, we offer a blind tasting at Eno every Sunday. Depending on how well you score, you can get some dollars knocked off the price or win a free bottle of wine. Our anniversary is coming up and we will be offering a very special gift to the highest scorer. Come in to see the WCWG and we can have some blind tasting fun!