In the U.S. we don’t normally use any form of address (any generic name) when speaking to a stranger who is our peer or classmate. Those forms of politeness have mostly dropped out of our language and our social customs, I’m sorry to say. Some of those formalities have lasted longer in certain regions of the country.
“Excuse me” is a customary opening. “Excuse me” and “Pardon me” mean the same thing when you are actually asking to be excused (such as when passing in front of or between people), but “Excuse me” is also a request for attention.
When speaking to a stranger in a public place, we might use “miss” for a youngish woman and “ma’am” for an older woman, “sir” for an older man. An older person might address a much younger one as “young man” or “young lady.” It would go something like this:
[In a theatre with reserved seating] Excuse me, ma’am, but I believe that’s my seat.
[In a department store, addressing another customer] Excuse me, miss, I think you dropped something.
[Anywhere] Excuse me, sir, could you tell me what time it is?
[Older person to younger person] Thank you for the help, young man.
If you are an employee in a service role, such as waiting on tables or helping a customer in a store, you use “sir” and “ma’am” or “miss” when speaking to your customers.