Japan came up with 5 situations that are "high risk" based on analysis of clusters. I'm going to make an executive decision and call them "5D"s (see below) for English https://twitter.com/imamura_kansen/status/1320471105354813440

1) Dinner parties with alcoholic beverages
Alcohol can lower your awareness and may result in carelessness. Especially in smaller spaces. (also my guess is that it applies to non-dinner as well, but the cases observed were people drinking at night)

2) Drinking & eating in large groups (more than 4) for extended period of time
Risk is higher when spending longer periods of time eating & drinking as opposed to short period. Especially in a larger group of more than 4, people tend to speak louder and increase transmission risk

3) Dialogues and conversations without masks in close proximity
There have been speaking/singing situations without masks that have resulted in transmission. Also need to be careful on public transit.

4) Dorms, shared bathrooms, etc. where people live in shared small spaces
Since closed spaces are shared by many for extended period of time, places like dorms are high risk.

5) Dressing rooms, break rooms, etc. where people go to take a break and become relaxed (and be less careful)
When people have a change of scene, they relax and let their guards down.

This is based on cluster occurrence data:
https://www.cas.go.jp/jp/seisaku/ful/bunkakai/teigen_12_1.pdf