Choose a recipe you'd like to make that requires activating yeast. The recipe should specify the amount of water needed to activate yeast. (Usually, this is approximately 1/4 cup). Place the appropriate amount of water into the measuring cup and heat in the microwave for a 10-15 seconds if needed. The water should be warmer than lukewarm but not hot. Aim for 110-115 degrees (think warm milk or a warm baby's bottle).
Water
Next, check the expiration date on the yeast to ensure it isn't expired. Add the specified amount of yeast to the water. Add 1 teaspoon of sugar to the water and yeast. Stir the mixture to combine.
Yeast, Granulated Sugar
Let the mixture sit, undisturbed, for about 10 minutes. The mixture should begin to look tan, foamy, and frothy on the top. If you started with 1/4 cup of water, the end result should be close to 1/2 of liquid including the foam.
After the yeast activates, follow the recipe as written.
Notes
*Please see post for additional information regarding yeast and troubleshooting the activation process. Step-by-step photos are also included.