This really opens a group and gets someone interested. I really wouldn't be surprised if there was already an opener like this one out there being used because, not to brag, but its really good I think.
Walk up to a target. This person could be in a group but should preferably be alone. This opener is useful for isolating a target from a group.
Walk up to this person and in a serious tone say
You:
"I have to tell you something / Can I ask you something?".
There are variations to the exact thing you say, as long as it is along these lines it should work. She will look surprised at first and say
Her:
"Yeah sure, what is it?"
At this point is when the opener gets effective. She is immediately interested because you are offering to tell her / ask her something about her.
At this point, look a bit remorseful / serious:
You:
"Actually... Never mind, I probably shouldn't. / On second thought, its not that important... / Actually its probably not such a good idea."
Right away she will be even more interested because it seems confidential and really important.
Her:
"Oh come on! Seriously, tell me! Anything at all, what is it? Huh? Come on! You suck! Tell meeeee...... plz plz plz plz !
:D:D"Point is, she is literally begging at this point for it. She is completely at your mercy in this interaction and you are in control of the conversation and her attraction. This will be sparking attraction.
Keep saying that you probably shouldn't tell her, maybe its not such a good idea, "on second thought...". She will be probing you increasingly as this goes on. It will sit in the back of her mind all day if you don't tell her.
Eventually, once she has begged for a little while (play with her a bit) you ask the question.
You:
"Alright, alright, alright! Wow, you are so demanding. [Neg]. Fine... here goes. This has been bugging me for a while now. Okay. What is your favourite colour? / When is your birthday? / What is your favourite TV show?"
You need to ask her something that is completely irrelevant and not important. This opener is similar in a way to Style's Floss or Brush opener, but you drag out the "I need to tell you something" part in order to increase attraction and keep control.
She will probably react like "Oh you suck! Are you serious? Wow, I hate you! God!" in a playful way. Tons of IOIs because you keep composure and use humor to play with her. Girls love this.