Added content to the "Performance" chapter.
Here you'll find the best practices which are usually ignored in real life Laravel projects.

Single responsibility principle
Fat models, skinny controllers
Validation
Business logic should be in service class
Don't repeat yourself (DRY)
Prefer to use Eloquent overusing Query Builder and raw SQL queries. Prefer collections over arrays
Mass assignment
Do not execute queries in Blade templates and use eager loading (N + 1 problem)
And more...

~DarkGravity