Yeast is a forgiving leavening ingredient. Warmer-than-ideal liquid temperatures may speed risings up a bit, and colder liquids may slow down rising dough, but it takes more than a few degrees variation in liquid temperature to cause any rising difficulties.
* Packets of dry yeast contain about 21/4 teaspoons of yeast. If you buy yeast in bulk, simply measure out the amount accordingly. Check the date on packets to make sure the yeast is fresh.
* The ideal temperature for a liquid that dissolves the yeast is between 95 degrees and 105 degrees. At this temperature the liquid feels comfortably warm to your hand -- neither too hot nor too cold. It is what I think of as lukewarm.
* If you are not sure if your yeast if alive and fresh, proof it by dissolving the yeast in warm water with a little sugar, 1/4 teaspoon or less. After about five minutes the water should look foamy. This "proves" that the yeast is alive and active and assures that the dough will rise.
* If the yeast dough has its first rising overnight in the refrigerator while you sleep, take the dough out of the refrigerator at least an hour before shaping it to bring it back to room temperature.
* If you're not ready to shape and bake a yeast dough, simply punch it down and let it rise again. The extra rising is fine. It will rise faster the second time.
* To prevent the dough from drying out while it is rising and to keep it moist and soft, rub it with butter and cover it with plastic wrap. Yeast thrives with gentle warmth and humid conditions.
* In a warm kitchen, yeast dough rises faster; in a cold or air-conditioned kitchen, the dough takes longer to rise. Since this makes rising times vary, use the rising time in the recipe as a guideline and punch the dough down when it has approximately doubled in size, looks light and fluffy and has a pleasant sweet smell rather than a sour, fermented one.
* Measurements given for flour are flexible since humidity and even the specific bag of flour used can affect the amount required to produce a dough with the correct consistency. When the dough feels soft and smooth, and is just dry and stiff enough to pull away from the sides of the bowl, it is the right consistency. On the other hand, a little more or less flour will not ruin a dough.
-- Elinor Klivans