The biggest thing is avoiding database structures that will be difficult to work with later, requiring data migrations to escape the dilemna. The book SQL Anti

The biggest thing is avoiding database structures that will be difficult to work with later, requiring data migrations to escape the dilemna. The book SQL Antipatterns is a good read on this subject. But realistically, I think you need to work in a few production databases and experience these problems before you deeply understand them enough to understand why they are antipatterns.