Not a list of slogans. One pull request from our billing code, the review comments it got, and the five rules that held up after years of reviews: names, function size, error paths, comments that explain why, and boring control flow.
One Terraform state for a whole environment meant 11-minute plans, fragile applies and an app deploy that could touch the VPC. How we split it into layers by rate of change and blast radius, passed values between them, moved resources with removed and import blocks, and kept the apply order sane.
We inherited an AWS account built by hand: 60 resources nobody dared to touch. Terraform import blocks with -generate-config-out let us adopt them in reviewed pull requests with a zero-change plan as proof. The workflow, the cleanup the generated code needs, and the traps.