its like an army mission my friend ....
the first thing u do is recon , check what she is doing eating? reading a book ? just chillin? and so on ...
Then you go for the kill...
like if shes is eating just go up to her and si hi , would u mind if i could sit down here i dont really like to eat alone it looks kinda depressing =p (but say it in a funny ****y tone cuz this is someway a little neghit on her aswell... )
then u play it from there , start up a conversation but seem totally cool like she is just another person not someone your trying to hook up with.... u can say: . dont you just hate (somekind of food u dont like ) thank god for this place , atleast you can get a decent meal here.... what do you think about ??? then in the middle of it you say your name and introduce yourself.... and go on from there.......
now if u want a scripted life then u are a looser , go around make your imagination run wild release yourself ( not in that way u freak! =P ) u cant just wait for everything to be perfect , something is prolly not gonna go as you want but you have to still remain cool at all time..... How can u learn if u dont make any mistakes..... ?
hope this helped....
Edt:
oh your 15 hmmm dont know how it would work on 14 -16 year old girls.... but this works well on 18 - 20++ girls