I always record a quick video walk round of the car and take some pics before mine goes back. I do this just incase there are any questions afterwards about the condition. Never had any problems but I’d rather be safe than sorry.
Other than that, as Glos Guy says, check the car out before you enter your pin and make sure everything is as you expected.
Finally and most importantly, enjoy your new car. Try and get a little review up once you’ve had it a while. Things you like, things that could be better etc