You can send an email to a new employee with a list of online course they need to complete, or you can meet face-to-face.
You can send a link to the corporate policy manual, or you can create job aids that ensure compliance with the policies.
You can write a code of conduct that reads like a bunch of rules, or you can describe the values you live by and the behaviors that go along.
You can keep the outcome of your investigations secret, or you can explain your rationale and show a fair and consistent process.
It should be clear that different processes lead to different cultural outcomes.
If you want a better culture, follow better processes.
If there is any part of your culture you don’t like, find the process responsible for it – and change it.