Any ideas on the most affective way of doing this? my situation is... The last time I went to this clothing store this really nice girl was working there who is often there and I managed to catch some interesting vibes when chatting to her normally as per the business sense ie talking about what shirt would best suit me.
It was interesting because I was initially being served by another girl and with my good strong positive posture I have been trying I locked eyes with her twice and it was on that second time she came over and asked me how my day was going?.
The reason I didn't get her number is because her boss was present in the area, but I know shes there and my plan is to approach her again tomorrow or on the weekend.
I was thinking about asking her what the best coffee shop in the mall is and then asking her if she would like to join me when her next break comes on, good idea ?

She's gotta hear you talk first bro.

Talk to her a bit at work... however, don't get her fired. Make sure its a good time to talk. You can ask her "Are you in work mode or talk mode?" and if she says work mode, she's probably either legitimately busy or she is just not attracted to you. That way you are not being some creep and you are also not being an asshole who is going to get her fired by continuously talking to her while she is at work.

If I were you, I would go back into the store and look for her to be available to assist you, then try on a couple of shirts. This should give you sufficient time with her to work some game, warm her up and gauge her interest.

You're giving her a reason to check you out openly as you try on the shirts and ask her opinions. If she has any level of attraction to you, it should be pretty clear through her body language. Its just a matter of triggering her reactions.

Just keep it friendly but flirtatious.

for example: ( after you tried a couple of shirts on)

You: which shirt do you like best?
Her: # 2
You: Why?
Her: I dunno, i like the color blue or it fits nicer ( blah blah-doesn't matter)
You: I see, so if you and I were to go on a date, I should wear a shirt that's blue ( or fits that way)
...........

If the signs are there, then confess to her. You're not really looking for a shirt you just wanted to buy some time with her without getting her into trouble so you could ask her for a coffee on her break or whatever.

Good luck dude.

_________________
Seduce their mind and the rest will follow.

Ok so I went there today and she wasn't there damn, the other girl was but she would be a 5 only because she had a swagload of makeup caked on, its kinda like abit of a turn off but I try not to be judgemental as I am sure shes got a nice personality.
Anyway so instead I went to another clothing store where I know really nice looking girls work, and I got chatting to a young slim girl who helped me find a nice pair of jeans that fitted me well ( considering I don't have a big waiste its very hard to get the right pair these days ) only problem was I should have sussed out that it was a busy shop and not chatted with her for so long and just got her number.
It was so busy she had to move from me to another shopper, ohh well the chat was nice lasted 3-4 minutes which I am happy about considering I never used to talk to any girls I didn't know during the day.
Its all about building yourself up and getting better, for some guys it takes longer to become natural at it and others they get it straight away.