A few examples:
There are clearly defined initiation rites for new employees that make them familiar with the engineering practices.
Focus is on a few key languages (C++, Java, Javascript, Python, Go) and code reviews are practiced over the team boundaries. This makes the knowledge transfer inside the company faster.
Changing your team and role regularly is encouraged.
Single, company-wide code tree and build system makes it easy to switch teams and make it possible to build very efficient tooling.
Coding style is strictly enforced to avoid petty fights and Google's very good coding styles guides include reasoning why certain choices were made.