This Neg works great:
"You have a really cute smile... yeah it's cute how the one side goes up a little higher than the other."
So simple yet so effective. I've field tested this with great results.
I got this one off of this site: www.sterlingslounge.com
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Yes i see the greatness in it.

That is a great one but telling her that her smile goes a little higher on one side isnt really a neg... however you have just lead me onto one that made me laugh my ass off as I thought of it.

You: I've been wondering who your smile remind me of and I just figured it out..
Her: Oh yeah, who?
You: William Shatner (the presenter from Rescue 911)

Later on during casual chat you can bring up "Did you know that the mask that Jason X uses is actually a direct cast from William Shatners face" (which it really is)
Clearly you want her to pick up on your neg and start trying to validate herself.

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Peace, Finchy!

It is a neg. A neg is something that you say where it seems to you (or rather, it is meant to seem to you) to be a compliment, but in fact knocks her self-esteem enough that she tries to qualify herself. It's like the false-nails neg; it's not an insult, not even teasing, but it works the same way.

Cool neg, mate.

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"Plan only what you must and live for the present - for tomorrow everything could change." - Personal Motto.

yep and this one knocks her by implying she isnt symmetric, which all women know is one of the keys to beauty.

in ragards to Finchy's comment i dissagree this is entirely a neg. said in an honest and seemingly harmless way it.

just remember guys that a lot of ppl r confused about what a neg is. its not an insult like "you are so noisy" thats just showing her that she has to lower her value because u say so.

. a neg on the other hand gives the target a chance to lower her value willingly. eg cute smile... one side higher" she will be thinking "its not an issue to him because him (the pua commented on it but is one side higher, does it look funny ect"

thats my two cents anyway