I'm an econ major who's interested in economics and psychology a lot...after PU of course...
One thing I stumbled across in my studies...is very relevant and useful in PU.
We all remember giving false choices (e.g. asking "Let's meet up is Friday or Saturday better for you?" instead of "Would you like to go out?") is quite useful.
But often times it seems a bit fake and in some situations u might find its hard to implement it.
Here is something imo more powerful and easy.
Set your preference as default(given) outcome and give her option to change it.
E.G. Let's say you have LMR.
Out of the top of my head: You can go smth like, "Tell me to stop if you want me to slow down. And escalate."
here we have both: false option which she most likely won't even choose.
If she's interested she won't tell you to stop unless you do smth very stupid.(or inappropriate/chody)
If she's neutral (but would rather take things more slowly) - She won't tell you anything (because of setting the fact that YOU WILL have sex as given"
If she's uninterested-she'll either tell you to stop, where you'll turn your escalation down a notch and try to get her hotter and build some complience
or
She'll tell you to stop even after you slowed down...then you are probably. better off stopping(cause chances are you didn't make your intent obvious/didn't sexualize enough/she has some "rules she really can't break"
The same can be used to avoid flakes. Rejections(although u prob. won't need this on approach itself) and etc.
Try it- see for yourself.
Where I learnt this from:
http://www.youtube.com/watch?v=JhjUJTw2 ... re=related
Also if you watch it till the end there are some other things you can implement
