Originally Posted by Piotr
Rehydrate! It was already discussed on this forum, bot it is worth repeating: if you don' give yeast a chance go get back into shape in clean water, you will loose ~50% of them.
Details on how? I used this method and it was just OK
5. Rehydrate the dried yeast. Although many people skip this step with fair results, re-hydrating it assures the best results. While you are waiting for the brew water to boil, rehydrate two packets of dried ale yeast. Put 1 cup of warm (95-105°F, 35-40°C), preboiled water into your sanitized jar and stir in the yeast. Cover with plastic wrap and wait 15 minutes.
Next, "proof" the yeast. Start by adding one teaspoon of malt extract or table sugar to a small amount of water (1/4 cup, for example) and boil it to sanitize. (A microwave oven is good for this step.) Allow the sugar solution to cool and then add it to the yeast jar. Cover and place in a warm area out of direct sunlight. Check after 30 minutes, it should be exhibiting some signs of activity - some foaming and/or churning. If it just seems to sit on the bottom of the jar, then it is probably dead. Repeat the rehydration procedure with more yeast. (See Chapter 6 - Yeast, for more info.)