Well you don't really need that as long as she feels that YOU are special. But it could be a great weapon if used correctly.
Giving them the feeling there special is basically done with sincere compliments. Key is to not give them much, but when you do make it really good. The delivery is very important.
For example, walk up to the girl, look right into her eyes, just look into her eyes for a LONG time and say, in a relaxed smooth voice, “You are stunning.” And whatever you say, mean it. If your voice isn't congruent with the power of your compliment, it will ring false. You need to deliver your compliment with either genuine enthusiasm, or genuine sincerity. It must have a driving emotion behind it, and not just be something that you’re saying just because you feel you have to. If you don’t feel that emotion first, and carry it through in your words and your nonverbal body language, SHE won’t feel it either. YOU have to lead the state first in order for her to follow. YOU must feel that state first for her to feel it.
Best is to compliment on something specific. Something specific about her would be more like noticing something she put a lot of effort into, something specific that most guys wouldn’t take the time to notice. For example, if she’s impeccably well dressed, you could give her a compliment about her clothes or style. Or something specific could be just a particular trait she has, like you could give a compliment on her particularly interesting green eyes.
Another compliment could be her smile: “I just couldn’t help but notice that you have the most incredible smile".
The second part of the compliment is to genuinely express to her the sort of feelings she’s whipped up in you, express to her the kind of reaction she’s caused you to feel. For example, “you just amazed me and I had to come over” is letting her know the kind of effect she’s had on you. You’re revealing your inner thoughts which is often more interesting to a woman than the compliment itself. And don't forget to pace the compliment.
Look her deep in her eyes, hold her close, then say: "Since I met you....you make me want to be a better man".