Use a checklist like the one linked below
https://www.mynewmotor.co.uk/dist/pdf/pdi.pdf
remember you are paying for the car it’s your money so take your time and ensure it all works if you are on your own get the salesman to sit in car and ask him to operate the controls while you stand outside to check lights etc
some cars get damaged in transit so check the car with a very beady eye
ask the question is there anything missing from the specifications
the car dealer is not your friend this is just simply a business transaction and you are buying a product it’s up to you to ensure that product is what it claims to be
take your time have a tea or coffee it should take a good hour or two to save any regrets later
and it’s not 100% right then it’s not right do not be fobbed off with anything the dealer says
you can walk away at any point until you put the pin in
Good luck enjoy it