How do you impress an unknown girl?

Answer 1

Talk to her.

You can't "impress" anybody unless you know them. How would you like it if a random person began to randomly show off to you? You wouldn't like it at all.

Just talk to her and be yourself, compliment her, make her laugh, ask her questions so you are showing you're interested in her.

Answer 2

Well, you pretty much have to know a lot about what they like, as in if they like to draw or something like that then you should show how good you are at it! Or, you just have to speak to her directly, without looking away or stuttering + blushing, looking her in the eye. Hope that this helps!

Also, you could make her laugh at something, this will let her know that you aren't shy at speaking!!