Where do you draw the line on the characteristics of new people to whom you introduce yourself?

Do you introduce yourself to friends of friends only? Do you only do it when you expect a long term friendship? Do you introduce yourself to your waiters and waitresses? Do you just do it to everyone whose cute?

And do you find where your the line is more stringent or relaxed than your perception of the average person’s threshold to introduce themselves to new people?

I always found it weird when people in TV shows would randomly invite mail men or strangers at their doorstep for coffee.

Otherwise, I’m always afraid I’m coming off too creepy/flirty for trying to be friendly.