Quote:
"Your such a little shit"
"Your short"
When she is talking "...are you done?"
Those are examples of Negs.
Playful vocal tone. If you act serious, then expect a "Fuck you."
Those are pretty bad negs. Really, they are just flat out negative statements. There is no compliment in there, back handed or not. There is no push/pull in the statement, nothing to create tension. "Did he just put me down, or was that a good thing? what the hell?.." is what you want her thinking. You can use full on negs like those above, but it really depends on the conversation situation, what was just said/happened, etc..
Better examples are all over the board, like
"Oh, you get funny dimples when you smile. That's so cute"
"Wow, I love your hair. Is it real?"
to name a couple classics from Mystery..
As for when to use them? Its guidelines.. You can stay with the 1-2 for a 7 or whatever, but I've been playing around with it lately, and have gotten some pretty remarkable results where Ive built attraction with a girl, but the whole time I'm negging the crap out of her, albeit in a very playful manner, all the while not making a single physical move on her at all. Three for three, I've had the girl just jump at me at the last minute and start kissing me strongly.