Start with what still works.
Does the spare key turn smoothly? Will the remote unlock the car even though it won't start? Does the deadbolt move when the door is open? These observations help distinguish the key, lock and doorway.
Keep access and repair separate.
If the hardware works but a spare has gone missing, ask about rekeying. If the door isn't closing properly, say that before choosing a new cylinder. For a managed or rented property, involve whoever can approve changes.
A local detail that helps.
Gateway Park and Bill Gentry Park are both on El Mirage Road, but they're different stops. If the keys are inside the car, the park name, nearby entrance and where you've parked help narrow down the location. For a house or business, use the street address and the door that needs attention.
And the garage?
Locks and opener controls are different systems. Describe which one needs attention.