Promoting the best trainer to manager is a common instinct, and a common mistake. Training ability and operational ability are different skills — the person you need is one who can make the front desk, staff, and renewals run consistently, not necessarily the person with the best client results.
Look for someone who documents, not just remembers
A good manager candidate writes things down — an SOP, a staff schedule, a note about a pricing decision — rather than keeping it all as tribal knowledge in their own head. That habit is exactly what lets a gym function when they're on leave.
Test their judgment on access and permissions
How a candidate reasons about who should have access to what — during the interview itself — reveals a lot about whether they'll manage staff roles carefully or just grant broad access because it's easier.
Give them real, scoped authority from day one
A manager role that can't actually approve a freeze request, record a payment, or adjust a schedule without owner sign-off on every single action isn't really a manager — it's an assistant with a bigger title. Real authority, properly scoped, is what makes the hire worth it.