Check the figures against your booking
The total, the deposit amount, the insurance package and the included mileage should all match what you booked. Where they differ, resolve it before signing rather than after.
Extras added at the counter — upgrades, additional insurance, equipment — should appear as separate lines you recognise and agreed to.
The clauses that matter
Excess and exclusions
What you are liable for after damage, and which damage is excluded from cover whatever package you bought.
Fuel policy
Which rule applies and what the supplier charges per litre if the tank comes back short.
Mileage
Whether the allowance is genuinely unlimited, and the per-kilometre rate above any cap.
Geographic limits
Where the car may not be taken — borders, ferries and unsurfaced roads are the usual restrictions.
Return terms
The exact time, the location and what a late return costs per hour.
Named drivers
Confirm every person who will drive is listed. This is the clause most often left incomplete, and it voids cover entirely if the wrong person is at the wheel.
Keep a copy
Take the signed agreement with you, or photograph every page. At return you will want to point at what was agreed rather than argue from memory.
Keep it until the deposit has cleared, not just until the car is handed back.