ER Diagram is one of the best method to create the database architecture.
1. Understanding the requirements of project. (If design and workflow is there then it will be very helpful)
2. Start listing all the entity required in the database.
3. Start creating relation between the entities.
4. Finally start adding attributes to the entities.
Finally, a important check will be start writing the select query on how to fetch the data for all the flow steps.
The goal is to ensure the smooth flow of data for each step.
To create entities with relation of m*n we use map tables.
Also, creating multiple map tables increases complexity in the database thus it is necessary to structure the database such that quering the db should not be a expensive operation.