I find that in order for things to have a chance to go relatively well with a moving woman on her way to do something (other than shopping n sh!t like that) she pretty much has to notice me coming her way. If I get eye contact or if she does that thing where she knows I'm there in her peripheral vision, but purposely stares straight ahead, I can tell she is "watching" me. These are my ques to make a move.
If I don't get those ques, I usually just let her go. I'm not the type to go blow up a chick from the word go without her noticing me. I'm sure I leave a lot on the table but I'm satisfied. I get mine.
I just hold out my hand out to my side about hip level, like I'm going to catch her if she were to keep walking. She sees this and eye contact is inevitable as she will look at me to see who the fvck I am (she's already noticed though). If she is wearing earphones, I just point to my ear. I always have a half smile with a slightly curious look on my face.
I always just say "Miss." in an audible and strong voice where there is no doubt I'm talking to her. Works way more times than not. I never stop looking deep into the colors of her eyes when we're talking. I can tell when she gets wet when I do this.
I win some and I lose some, but I keep playing.