I guess it just happen naturally.

Unker got only a handful of experience amoi stranger approach me in public and its all happen during ma shopping for grocery.

1) I was holding a can of jam reading the ingredient. Out of nowhere amoi poup and show me another can, telling me thats better, suggesting me to try.

2) I was pushing ma trolley around, passing by one amoi few time, each time got make eye contact (obviously because she quite cute). Then when I was at one lane looking for staff she came approach me asking me where I get one of the item in my trolley.

I guess you can try the menthods above to approach amoi you fancy in public place. Then you can establish common topic to talk.

Good luck