For a developers to know
1. Set up a local IDE with a full clone of the app (frontend, backend, DB).
Thus the app must be fully able to run on a small, local environment, which is true of open source apps but not always for for-profit companies
2. Use .env or similar to manage config/secrets; never commit them.
A lot of people don’t properly exclude secrets from version control, leading to catastrophic secret leaks. Also when everyone has their own copy, the developer secrets and credentials aren’t that important.
3. Debuggers and breakpoints are more scalable than console.log. Prefer conditional or version-controlled breakpoints in feature branches.
A lot of people don’t use debuggers and breakpoints, instead doing logging. Also they have no idea how to maintain DIFFERENT sets of breakpoints, which you can do by checking the project files into version control, and varying them by branches.
4. Test & Deployment Environments Maintain at least 3 environments: Local (dev), Staging (integration test), Live (production).
This is fairly standard advice, but it is best practice, so people can test in local and staging.
5. Make state cloning easy (e.g., DB snapshots or test fixtures).
This is not trivial. For example downloading a local copy of a test database, to test your local copy of Facebook with a production-style database. Make it fast, eg by rsync mysql innodb files.