Ask any agency these five questions before you sign.
Do they own their data and tools?
An agency renting the same software everyone else buys competes on the same inputs, so the strategy is a commodity too.
Do they price on cost per acquisition?
Activity is easy to bill. The number that matters is what it costs to win a customer, and whether it is going down.
Can they show verifiable proof?
Ask for named results that trace to a real analytics or ad account, not a vague claim or a stock screenshot.
Who actually does the work?
Ask whether you work with the people doing the work, or an account manager relaying messages.
Are you locked in?
Ask about contracts. The results should be the reason to stay, not a clause.