All changes to Launchpad need to be reviewed and approved by a reviewer. Most changes should have that reviewer be someone other than the author of the change. Changes made by a reviewer who is confident that the risk of the change being harmful is less than the cost of having it reviewed may be landed without a second reviewers feedback. Our goal is for every Launchpad developer to also be a reviewer, and to that end we have a mentoring process to initiate new developers onto the review team.
Here are resources we've established to help reviewers: