Basically i found you cant, cause no matter how much u practise u will always find a girl, who reacts differently to what u where exspecting its gunna happen eventually...
so heres my advice or the way i approach things, try not to use to many lines cause they can always crash leaving u stuffed...
Secondly and this is the "BEST!!!!" peice of advice i can give u, keep women in your life!!! even if u friend zone these girls (they like u and u dnt like them!), keep them in yr life on a short lead, anything your unsure about use on these girls see if it responds well or not
and see how they react to it, this will give u a better idea on how actually girls will react to YOU saying it...Thirdly, it might sounds sad but if your this worried practise in a mirror, jst to make sure yr stood right u sound real and not fake, and yr facial expressions look inviting and kind without seeming fake and wierd ....