New Year's
American kids expect candies on Halloween, and Chinese kids usually cheer for red envelopes during the Spring Festival period. If a friend with kids visits during the period, or if you visit, it is nice to give a red envelope to the child for luck. The amount depends on how close you are to the parents. It's usually around 100-200 yuan.
Weddings
If you are invited to a wedding, you must prepare a red envelope with your name on it - it will be logged. Again, the amount depends on how close your relationship and local standards.
In Shanghai, it is usually 300-500 yuan for a regular friend or colleague. If you go with your lover, the two of you will give around 800-1,000 yuan. You can always give more to a close friend. After all, it will all be returned on your wedding.
Avoid giving 400 yuan as the number four (si) sounds similar to the word for death in Chinese. Many people avoid odd figures like 300 or 700 because the even figures indicate sticking in pairs, like an enduring marriage.
Birth of a child
The birth of a child is usually celebrated with a feast when the baby is one month old. Parents usually only invite relatives and close friends. Either gifts or red envelop cash are welcome.
Similar to the nuptial situation, your money comes back to you when you have a child. If you've already had one child, then maybe you already received money.
House moving
House moving/house warming parties are common occasions for required renqing. It is more common to give useful gifts. Many people also buy coupons from electronics store as gifts.
(Shanghai Daily January 19, 2009)