car hire

hi all,we were thinking of hireing a car for 2 or 3 days and was wondering if there was any do,s and donts, like do we need to carry our passports with us.lots of friends trying to talk us out of it saying the standard of cars are bad but assured them that icr hire cars are of a good standard.all help and advice appreciated thanks. oh yeh,hoping to go up to alu deniz