Fresh yeast will keep for up to two weeks in a plastic storage box in the refrigerator. The box should have a tight lid in which you have made a few small air holes. There should be enough holes to prevent any condensation, but not so many as to overexpose the yeast to air.
The yeast should be a creamy beige, smooth and in one piece. Yeast that is dry, crumbled and grey is stale and will not work. Dried and instant rapid-rise yeast should be stored in a cool and dry place. They will keep almost indefinitely, but try to observe the 'use-by' date on the packet. If you use it after the expiry date, check that the yeast foams after it has dissolved. If it does not, the bread will not rise properly.
** Asian Online Recipes