How to start to talk with a native speaker naturally?

Discuss the weather.

Where do you start a conversation with a stranger?
You just don´t walk up to someone and ask questions.
So where?
In a public tranportation.There you can ask about the sights in the city even if you know them, or in a train about the places you pass, if you are allowed to borrow the newspaper.
In a cafe ask at the next table what they would recommend
At H&M ask a girl of your age to help you pick out one of the outfits you are trying on.
Supermarket - look confused and ask a senior citizen about the local cooking and if she could please help you come up with some ideas.

Some foreign visitors come to China and how to talk to them?

Not British is also OK?

People love to talk about themselves.

The easiest way is to notice something about them, and point it out to them, or ask them about it.

When I was a little girl, I liked to pretend I was Dick Cavett, and tried to get them talking. It really did work best when I got them to talk about themselves.

If you want to talk to tourists you have to think about who it should be,
Stick with women and preferable in your own age group or older women.
If they talk with someone else you can say excuse me and ask what language they are speaking, where they come from, what made them come to China etc.

I personally would be very careful in giving an unknown person a compliment about something she wears. It can be misunderstood and some will feel it is far too personal.