

Get a pirate hat. Wear that pirate hat. If they start the convo, quickly let them know you are on the lookout for more booty.
On a more serious note, other than having something interesting to talk about (dog, coloured hair, pirate hat), be sure to watch the eyes and try to hold eye contact with people who interest you first. We look at things that interest us. But please don’t stare!
Longer than one second is basically a big sign of interest, so maybe crack a smile. IF they are super interested and confident, chances are good that they will approach you.
Good luck, sailor.
Rarely in Europe.
If there is the Football World Cup or Euro Cup, you will see flags in European Cities and People wearing them are not uncommon.
During a random Tuesday, this is very uncommon as people tend to remember in which country they live without having to be reminded.