Confirm the desk is actually open
A supplier being described as 24/7 does not always mean the specific location is. Check the opening hours for your exact pickup point and your exact arrival time.
If the desk closes before you land, ask what the alternative is: a meet-and-greet agent, a key box, or no handover until morning.
Expect an out-of-hours fee
Many suppliers charge a surcharge for handovers outside standard hours. It is usually modest, but it should be visible before booking rather than appearing on the final bill.
Ask whether it applies to the return as well — night drop-offs are sometimes charged separately.
Give the flight number
This is the single most useful thing you can do. Suppliers that track arrivals will hold the car through a delay; those that do not may release it after a fixed wait.
If the flight is badly delayed, contact the supplier directly as well as relying on tracking.
Inspecting a car in the dark
Night handovers are where undocumented damage most often slips through. Use a torch or the phone flash, photograph every panel and wheel, and do not accept "it is already noted" without seeing it written down.
If the light is genuinely inadequate, note that on the form and re-inspect in daylight, sending the supplier dated photographs the same morning.