Start with very cold whole milk. The cooler the milk, the more foam you can make since you'll increase the amount of time you can steam it.
Fat and protein are really important in foam quality, so whole milk is ideal for steaming. If you want to use soy or almond, you'll have to aerate the milk more.
First turn on the machine. Once it's at temperature, purge any condensed water out of the steam wand by turning the steam on and off for just a second. You don't want that water diluting the milk.
Next, stick the wand just under the surface of the milk and turn it on. Allow the wand to "breathe" in the milk, incorporating small amounts of air as you heat.
The wand should enter the milk at a 60 degree angle, so that the milk circulates around the pitcher.
Circulating the milk is important for evenly distributing air bubbles, and making sure they're of similar small size.
You'll want to incorporate all of your air before the milk reaches 90°F. If you continued to aerate after this temperature, you'd start to get big foam bubbles which aren't ideal.
Once you get to 90°F, bury the wand deeper under the milk so it's no longer hissing. Continue to heat until the milk reaches around 135°F.
Next tap the pitcher on the counter to release any large air bubbles. Now swirl the milk and the foam together for 10-30 seconds to incorporate the foam uniformly throughout the milk.
Now you can pour into your coffee or espresso and enjoy perfect, beautiful foam!