a DHV could be a story where you (in passing) mention a "girl you were seeing", that time you were on your yacht, that time you were in some exotic country, that time where you did something good like stuck up for your friends, came through for your family, or something else. As long as it doesnt come off as bragging.
Or it could be just displaying that you have a skill that noone else has. Cold reading can be a DHV. Like the ringfinger routine or the cube.
In addition, you display DHV by not being like 95% of the other guys whos tried to talk to her lately. Youre special. Having your arms around another girl or two as you open the set is also a DHV. In this case, a pawn could be a good idea unless youve got a pivot. Being the center of attention is also a DHV. If she sees you at the centre of a set, making everyone laugh and have a good time, then you merge that set with ANOTHER set, making THEM enjoy themselves as well, thats also a DHV.
Hm... DHVs are everywhere
As for negs, i think Mystery lists quite a few in his book. I seem to recall that. In any way, negs are just one way to IOD a girl, to remove her assumption that youre trying to hit on her, and in turn making her curious about you. For instance i just saw a little clip of mystery negging a very nice looking girl.
He basically said "well youre beautiful, but its Hollywood. Beauty is common. But you seem charming and bright, so you know.. two out of three, thats pretty good", then later he goes "who are your friends?" she replies "oh theyre people i work with". Mystery asks "oh, so what do you do?". "Im a model", she says, leading into Mystery going "oh.. like a hand model?". She says "No, im a lingere model".
Later she asks "if im so awful, why did you speak to me?"
Mystery: "honestly?"
hb: "yeah"
Mystery: "proximity."
hb: *laughs* "oh thats nice.."
Then he takes her with him and sits down with her.
Fun to watch, negging at its best, and using classic negs.
But as far as i understand it, and im not even out of my AFC shell yet, negs are just small IODs meant to lower her own percieved value, in order for her to lower her bitchshield and start to wonder about your intentions.