Сommon

Developer's

Mistakes

Over complications

tools, lib deps, approaches, use as many patterns as possible

Useless abstraction

abstract ORM, IoC, etc

DRY

WET, PRY

Wrong layering

Split by feature

Huge source code files

split by functionality, no more than 250loc, 2 screens

Premature optimization

Clear code, optimize on demand

Unit test discipline

Implement through unit test runs not UI