People in Japan hold ceremonies known as kei-cho (kei stands for congratulation, cho for condolence) for special occasions which are collectively called kan-kon-so-sai: kan stands for turning points of life such as birth and coming of age, kon stands for marriage and wedding, so stands for funeral and memorial ceremony, and sai stands for annual celebrations such as New Year’s Day, mid-summer Bon Festival, July 7 Tanabata Festival and Shichigosan (literally meaning "seven-five-three," for celebrating children’s growth). Among these, kon and so ceremonies in particular have many rules and practices to be observed. You may feel more comfortable about these by asking for a brief explanation from older Japanese acquaintances.
When a close friend is having a celebratory event such as marriage, birth, employment or entrance to school, there is a custom for you to present goods or money. For giving money, you put it inside a special envelope called shugi-fukuro.
When attending funerals, men wear black suits, white shirts and black ties. Women also usually wear black. For sending money, you put it inside a special envelope called fushugi-fukuro and hand to the receptionist. Details for funerals and weddings can vary depending on the religion, so it is best to seek advice from people familiar with the ceremonials.

* Details can vary depending on the religion and the region