i believe that most of the day game must be indirect game because for the girl it feels kind of awkward at first, of course you totally look like you're hitting on her and that might cause you more problems. now if you're dealing with Approach Anxiety and you're opening just for that reason, any opener will do as long as you release the outcome.
just go for the simple hi or a hey what's up
in the subway (depending on her mood but try it, if it works it will crack her a smile it all depends on the delivery) hey don't go falling down the rails i don't wanna be late for work(smile)
and do C/F for a while also, use assumptions instead of asking personal questions for example say umm you look like a Sharon or an Adrianna to me
No, just no.
Keep indirect for night game. Day game is Direct Game.