People who bake at home typically use one of three types of yeast: fresh active yeast, instant yeast or active dry yeast. People often prefer active dry yeast because it is less perishable than fresh active yeast but provides a deeper flavor than instant yeast. Because active dry yeast can lose its rising ability over time, you should activate the yeast before adding it to a recipe to ensure that it is active and will provide the needed rise in your dough.
Measure 1/4 cup of hot tap water and pour it into a measuring cup that holds at least 1 cup.
Check the water temperature with a thermometer and either wait until it cools to between 100 and 110 degrees Fahrenheit or add cold water to lower the temperature. If you add cold water, pour some water out to get back down to 1/4 cup before proceeding.
Stir 1 tsp. sugar into the water, if desired, to activate the yeast more quickly. Recipes that do not call for sugar should skip this step because it might make the bread too sweet.
Stir in 2 1/4 tsp. of active dry yeast into the water. This is the amount contained in a 1/4 oz. envelope of packaged yeast.
Wait 10 minutes while the yeast foams. If the yeast has not foamed up to the 1/2 cup mark on the measuring cup, it is too old and will not work.
Prepare the bread dough as directed in your recipe. If the recipe does not call for activating the yeast beforehand in 1/4 cup of water, subtract 1/4 cup from the amount of water the recipe calls for to account for the water you used with the yeast.
Knead the dough according to the recipe. Typically, recipes call for you to knead the dough for about five to 10 minutes, or until it is smooth and elastic in texture.
Place the dough in a greased bowl and cover with plastic wrap or a damp cloth. Set the bowl in a warm location for one or two hours, until the dough has doubled in size.
Follow the remainder of your recipe's instructions for allowing the dough to rise more, shaping it and baking it.