Ratio and temperature
Sift 2 grams of matcha, about two heaped chashaku scoops, into a warm, dry chawan. Pour 60 to 70 milliliters of water at 70 to 75 degrees Celsius. This is the ratio Ippodo and Marukyu Koyamaen recommend for most of their drinking grade blends.
Whisking
Hold the chawan steady with one hand and the chasen lightly with the other. Whisk in a quick W or M motion from the wrist for 15 to 20 seconds, keeping the tines just above the bottom of the bowl rather than scraping it. Stop when the surface is covered in fine, even foam without large bubbles.
Finishing
Draw the chasen across the surface in a slow circle to pop any remaining large bubbles, then lift it straight out of the center. Drink within a minute or two while the foam still holds and the temperature is comfortable.