if youre talking to a girl and it seems like she is in to you, and you into her then the next step is to:
A.) Ask her out on a date.
if youre talking to a girl and it seems like she is in to you, but you dont want to do the dating scene or take things serious aka "just fool around" then:
B.) flirt harder, make yourself sexually appealing, act more "alpha", build up what some call "kino" (look that shit up dude), be a little more touchy feely, but not in a creep way. smile smile smile. youre a witty and clever guy, right?
Overall tho, be smooth, laid back, aloof, dont try too hard for their attention, make them work for yours.
If theyre really into you they will be seeking your attention, once they show those attention seeking signs its your game now and the ball is in your hands -- play it smooth, proceed with step A or B.
And if you fail miserably dont show that shit, act like you got chicks lined up. they think your somehow special if you have other girls attention.