Yeast makes carbon dioxide gas that acts as a leavening agent. Start by "proofing" or growing the yeast: this ensures it is active and re-hydrated (this step is not required for fresh or instant yeast):
* Sprinkle the yeast onto warm (110 degrees F/45 degrees C) water and stir to dissolve. The water should feel warm, not hot, to the touch. Yeast feeds on sugars--honey, molasses or refined sugar--by breaking down the flour's starches into sugar molecules.
* Set the yeast aside until the mixture resembles a creamy foam. This should take between three to eight minutes.
* If nothing happens, discard the mixture and try again with different yeast.