When you meet a stranger,what will you say first?

Irene it depends upon the circumstances of the meeting. Often it's something neutral but pertinent: "Hi, I'm Dale. Our host certainly has a buzz on, doesn't he"

If you don't like "Hi," then maybe "Wow," or "Gosh"

well.Thank you.

When English is not your first language, conversations may be a little difficult to sustain at first; however, the same dynamics apply as would be in your first language or culture. It'll be a little tougher because you need to simplify things to make it easier on yourself to reply back.

As an example, I'd say:
" Hi..my name is Irene. What is your name?"
"How do you know the host?"
or
" Where are you from? I'm from France."
or
"Do you like dancing?"

"What do for fun/entertainment here?"

All of what you discuss highly depends on the social setting. Ask some questions about the person you're meeting without being too invasive.

If the first thing you say to someone is they might be too dull don't expect the rest of the conversation to go well.

I find a sincere small compliment works wonders.

When you first meet the person, notice something attractive about them, for example their shirt or dress, and compliment them on it, making it about them.

Rather than saying "that's a cute dress" say "The color or that dress really suits you. You look great in it."

Back to the original post, of course the first thing you would say to a person upon first meeting them would be "hello" or some such. That's not dull. If someone said something off the wall to me, I'd be hesitant to talk to them.

Not at all, Irene

Everything becomes "dull" and mundane when extensively used, I guess. Around here, one standard greeting is "zup?" (a contraction of "what's up?).
Note that it takes the form of a question, as opposed to being merely a salutation. Other examples might be:
1. How ya doin?
2. You doin all right?

Such greetings are intended, I guess, however superficially, to express some "concern" with what the other person thinks, or how they feel, and are presumably more likely to elicit a more "meaningful" response than a "hi" in return.