1. Funeral wake
通夜
In Japan, to express sadness over someone's death, Japanese use phrases such as ○○さんがなくなった。(“Mr. ○○ has passed away”), or ○○さんに不幸があった。(“Mr. ○○ had a misfortune”). A wake is a ceremony held the day after someone dies.
For this you should dress as plainly as possible. If it is a co-worker's family, the condolence amount(香典) is generally between 3,000 and 5,000 yen. The main difference from other rituals is that new bills are avoided. Condolence bag can be purchased at convenience stores as well as black ties.
At the reception desk, we hand over the condolences while saying, このたびは、ご愁傷様です。(“We apologize for your loss”) and 心よりお悔やみを申し上げます。(“We would like to express our deepest condolences”). There is a notebook for you to write down your name, address, etc.

2. Flow
流れ
There are two events to attend: the wake and the funeral. It is preferable to attend both, but it is sufficient to attend only one.
After expressing your condolences and giving a condolence gift at the reception desk, you will be led into the ceremony hall. There are many chairs(椅子) lined up, so take a seat. It is a good idea to sit towards the back so that those who had a close relationship with the deceased are in the front.
In the Buddhist ceremony, you will spend some time listening to sutras(お経) and the chief mourner's greetings. You will then be encouraged to burn incense. If you don't know how to do it, just watch how the person in front of you does it.