Dissolve dry yeast in water warmed to 100° to 110°–this step is also called proofing. It's always a good idea to use a thermometer to measure the temperature of the water until you feel comfortable recognizing the target temperature. You can also test the warmth of the liquid on your wrist–it should feel no warmer than a hot shower. About 5 minutes after mixing the yeast with the warm water, the mixture will start to bubble. If it doesn't bubble, the water was either too hot, which killed the yeast, or too cold, which inhibited its growth.
Note: Glass bowls and wooden spoons are preferable to metal ones, which can react with the dough and affect the bread's flavor.