If you haven't already, I'd reccommend reading my post. (:
living-in-the-flow-vt56529.html
My mid game usually just consists of a lot of teasing, cheekiness, flirtyness, deliberate play on boundaries, showing that I'm not scared of potentially awkward topics/situations, etc, kino(this should run through from opener), erm, I dunno, I do a WHOLE lot in mid game, but it is stuff I do naturally.
Typically, depending on what method you use, you want to be breaking rapport (teasing does this), you need to be getting her to qualify, and sexually escalating. Just be natural though, enjoy the interaction, and enable the girls to enjoy the interaction. I like Cheeky/Flirty as opposed to Cocky/Funny, cos it often gets the girls to blush feeling all 'naughty' and what not. I usually have pretty successful midgame.
Closing is another thing, if everything is running smoothly from opening through mid game, the next stages should come naturally, don't second guess yourself. Second guessing WILL fuck you up.
For example, say you have oppurtunity to kiss a girl, and you hesitate(the second guess), she will likely sense you are nervous etc, and this *could* potentially ruin things.
Just go with the flow, bro.
~Liquid Blend