I'm planning on trying out my first ever approuch tomorrow and it will be day game to kill some time before I meet with friends. I'm planning on using this opener but don't know what to follow it up with.

I'm probably going to use a time restraint, with the following.

"Hi there, How's it going, this may sound a little random, but I just noticed you and I had to come over and say hey, how's it going? I'm bla bla. Again, I know this is strange, but it's very rare you see a stunning girl like you walking down the street. So what's the story, what your name? Nice to meet, so what you got going for you apart from your looks?"

Any advice on what I can follow this up with to keep the conversation flowing, then eventually number close?

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Those who push themselves, and are willing to face pain, exhaustion, humiliation, rejection, or worse, are the ones who become champions.

this is like the pussified version of an Alex Coulson approach which will effectively serve to turn any girl off between explicitly introducing a negative vibe and complete awkwardness

My I suggest just:
your also trying to qualify her on an opener before she has shown any interest? You should really save your canned material until after you have opened.

I am not sure where you've found that opener, but DO NOT NOT USE IT. It's weak and for so many reasons.

It's too long, if the chick has no immediate physical attraction to you she can easily lose interest in what you are saying( especially if she is with other girls) The word "strange" is brought up twice, (not painting a good picture). Then! the last part is the worst part, you are challenging her, if she perceives you as confrontational or arrogant and she doesn't have a physical attraction to you, it's game over.

There's nothing wrong with challenging a woman, it's a great way to escalate. However! the beginning is not the time for it. You haven't given her a chance to scope you out.

If it's routine you must do, make it something funny and go from there. It's one thing to say certain things to a girl. but it's always wise to at least try to have her state of mind in a welcoming and happy state. A laugh is the best way!

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Seduce their mind and the rest will follow.

I dont think I would use that. It seemed very awkward. Id drop that for a simple "Hey I just noticed you, and decided I didnt want to miss the opportunity to say hey." Ive also read on numerous occasions not to give your information away. And this I found to be kind of desperate, like you are trying wayy to hard.
To get her number make it clear in the conversation that you will be meeting friends shortly, and at some point while talking hand her your phone and tell her to put in her number. (Most girls that would decline just from you asking, feel sort of obligated once the phone is in their hand)

Best of luck to you