One: documented process
Ask to see the actual build and QA checklist, not a description of it. A team that runs campaigns at volume has written procedures because memory does not scale. If the answer is "our people are experienced," you are buying individual habits rather than a system.
Follow up: what happens when the person who normally handles our account is out?
Two: account and data ownership
Your ad accounts, pixels, and audience data should belong to you, with the partner holding access rather than title. This single term determines whether leaving is an administrative task or a rebuild.
Get it in writing, including what happens to historical data on termination.
Three: security practices
Who on their side can log into your accounts, how access is granted and revoked, whether credentials are shared, and whether multi-factor authentication is enforced. Ask about subcontractors specifically — the honest answer is often yes, and yes is fine if it is disclosed and governed.
Four: turnaround commitments
Concrete numbers, not adjectives. Time to first launch from an approved brief. Time to implement a change request. Time to respond to something broken on a Saturday. A partner who cannot state these has not measured them.
Five: communication cadence
Who you talk to, how often, and through what channel. Named humans beat ticket queues for anything urgent. Beware the structure where the person who understands your account is not the person who answers your message.
Six: conflicts and exclusivity
For agencies: non-competes, non-solicits, and whether the partner works directly with businesses in your clients’ categories. For businesses: whether they run your direct competitor two towns over, and how that is separated.
None of these questions are hostile. All of them are answered easily by a partner who has thought about them, which is exactly the information you are gathering.