In my experience it should go a bit like this:
You "Hello there, are there any vacancies going here?"
Person: "Yes there are, do you have a CV?"
You: " Yes (You will hand over a CV in a plastic pocket) here you are. My contact details are on the top and you can contact me anytime"
Person: "Ok brilliant, we'll be in contact with you soon"
You: *smile and look courteous* "Thank you so much for your time, have a nice day"
** If they don't have opportunities going. You should hand over the CV for future reference.