Who will actually run the account?
Ask who logs in each week and makes the changes. In some agencies the person who sells you the service never touches the account, and it's handed to whoever has capacity.
For a small or mid-sized business, you want to talk directly to the person managing your campaigns, and for them to know your business well enough to spot a bad lead.
How are they paid?
Many agencies charge a percentage of your ad spend. That's simple, but it means the agency earns more when you spend more, even when spending more isn't the right answer.
A fixed management fee removes that conflict. Whichever model you choose, make sure you understand it before you sign, along with any setup fees and minimum terms.
Will you own the account?
The Google Ads account should be in your name, or at least owned by your business with the agency given access. If you ever part ways, you keep the history, the data and the conversion tracking.
Be cautious of any arrangement where the agency owns the account and you'd have to start from scratch if you left.
What do they count as a result?
Clicks and impressions are not results. Ask how they'll track phone calls, form enquiries and bookings, and how they'll make sure the account optimises towards those rather than cheap traffic.
A good agency will check your tracking before doing anything else, because if the tracking is wrong, every decision made from it is wrong too.
How often will they work on it?
Ask what happens in a normal week. You're looking for search term reviews (and blocking the irrelevant ones), budget and bid changes, ad testing and a look at the landing pages.
An account that's only touched once a month tends to drift towards Google's defaults, which rarely suit a small New Zealand business.
Will they tell you when not to spend?
The best sign is an agency that's willing to say Google Ads isn't the right channel yet, or that your website needs fixing before more money goes into ads.
If every answer is a bigger budget, keep looking.