Lmao at approach 1.
Anyone can go up to some girl and ask a random question. What you did is no different from asking, "what time is it?", except it's more awkward.
In the situation you were in, the thing to do is just plow until one of the two girls gets receptive. I'm guessing they weren't too thrilled when you opened them, but that doesn't mean you should dissappear already.
Approach #2: Your conversation was lackluster. When you asked her how her summer was, and she gave the 1-liner, you should have pushed it a little. "What did you do?", "any good stories?", etc. Once she gives you something small ("i was in peru/bahamas/working as a stripper"), you pounce on it and follow up.
Also, don't talk about work. You can talk about school, since you're both students at the same place, but even then in moderation. Talking about work, esp. how much a job pays, is a little over-the-top, most people don't like to talk about their salaries.
Approach #3: Don't number close with a coworker standing with there. She's almost certainly single and getting fvcked by two different guys right now, but you got rejected because you tried to number close with no rapport.
All you did was complement the store (I don't even know what the purpose of that was), then ask her for her name and how often she's working. That's not enough for a #-close. Maybe if you were social-proofed, or had a good opener, or something, but in a generic situation like that, you need more than "what's your name."
I suppose that practice makes perfect, but you should really take these tips to heart. You are racking up all these rejections because of errors in your social intelligence. You should be getting rejected because the girl isn't into you from the start; those are the cases you can't help.
