How I design a database schema before writing any code

Most of the worst bugs I have shipped were not logic errors. They were modelling errors that logic had to work around.

I start with nouns. What things exist, what does each one own, and what is true about it at every point in time.

Then I write the awkward queries first. If a query the product obviously needs is hard to express, the model is wrong, and it is much cheaper to find out now.

Only then do I write a line of application code.