While the brewer takes all the credit for a great beverage, it is actually the yeast that does all the magic. Unfortunately they are least understood.
1. always store them in a cool and dry place. dehydrated yeast has a six to 18 month long shelf life, but once hydrated they either need to feed or they die.
2. If you happen to keep them refrigerated, then either consume the whole packet in one go or wait for an hour for it be in room temperature before opening the sachet.
3. Always pitch the yeast at room temperature for 15 minutes in sugar solution before adding it to your wort or must. This way atleast you can be sure that active yeast was used.
4. Keep some backup yeast with you always. Yeast are temperamental creatures and create a lot of unique variance.
5. Unless you like the stressed yeast sulfide smells in your brew, it is advisable to use either some yeast nutrients or yeast energizer.
6. If you still happen to get some sulfide smells, clear it using copper sulfate. (don't overuse)