Irrelevant. The opener itself is basically anything that "opens" her attention to you. What matters is what comes AFTER the opener. And that follow through can be totally random too.
For example,
"excuse me i'm looking for... [pause + deep eye contact] you know what? actually scratch that.. who knew i'd ask a girl my type for directions, it's so weird, who are you and what are you doing to me? you sneaky little dark eyed blondes.. the same thing happened when I was in xyz lately...". You keep talking and let her say something back until something hooks well.
you can even say, [when you STAND near each other]
hey! is this?... [as if you noticed something about her clothes/gadget/etc].. umm.. [pause act embarrased].. sorry never mind, sorry, i feel so stupid to bother you.." [but keep eye contact]. she will say "no it's fine what is it?" and will encourage you to talk. then you can pick something on her, just anything, and use it to talk about it whatever you can, like, where it comes from, what it means when women wear it, only x type of girls like it, that your sister bought that right after breaking up with her BF, you can change topics like snapping fingers and it's fine.
If you want to practice it then do it with girls you know. When you talk, start talking about X, then at any random moment cut it by introducing another topic, talk talk talk, then again, cut, another topic etc. No smooth transitions, no explanations, no intros. Just new thread, cut, new thread, cut, new thread, out of nowhere. You will see they will go along with it as long as what you talk about is not boring. Don't do it with guys. Guys will think you're insane