in the middle of a conversation she is enjoying:
you: are you dating anyone ?
her: no bla bla bla
you: *with a fun playful manner* why? is it because you are really fussy;)?
her: bla bla bla
you: ah yea i can see that about you lol. if i asked you to come out with me this weekend what would you say

?
if she gives a positive response you should be able to figure it out from there, if negative you can reply with something like "i didnt say i was going to ask you out lol" and plough on. its as simple or as complicated as we make it really.