The short answer: Use a tulip-shaped glass, look at the color, smell it gently with your mouth slightly open, take a small first sip to get used to the alcohol, then a second sip held on your tongue, and notice how long the flavor lasts after you swallow. Add a few drops of water and taste again.
1. The glass
A tulip-shaped glass, like a Glencairn, gathers the aromas at the top. A rocks glass works, but you'll smell less.
2. Look
Color hints at age and cask, but it isn't proof of quality. Swirl and watch the "legs" run down the glass: slow, thick legs usually mean higher proof.
3. Nose
Bring the glass up slowly and breathe in gently, with your mouth slightly open. Don't push your nose into the glass; the alcohol will numb it. Common notes: vanilla, caramel, baking spice, fruit, oak, smoke.
4. Palate
Take a small first sip just to get used to the alcohol. On the second sip, let it sit on your tongue for a few seconds. Is it sweet, spicy, fruity, nutty, smoky? Is it thin or rich?
5. Finish
After you swallow, notice what stays and for how long. A long, evolving finish is one of the marks of a great whiskey.
6. Add water
A few drops of water can open up aromas and soften the heat, especially at higher proof. Taste again and compare.
Taste side by side
The fastest way to learn is to taste two whiskeys next to each other, like a bourbon and a rye, or the same bourbon at two proofs. Differences jump out that you'd never notice alone.