i often find it beneficial to start with a number of sentences describing your objects before you start designing tables and relationships - then you can check off that your schema matches your requirements
for example
There are many people
many people can be students
many people can be employees
a person may have many addresses
a person may have many telephone numbers
can a person be a student and an employee at the same time?
as simple as this is it really helps to design a database
MVDBA