I know that in general, when seducing a girl it is crucial to eventually sexually escalate with her in order to end up sleeping with you. Of course, I would start to sexually escalate with the girl on the first date, assuming I got a first date with her. However, when I approach a girl whom I just meet for the first time and I am trying to just get a first date with this girl, then do I have to sexually escalate with her before I ask for her number in order to not a get a flaky number from her or do I just need to build enough rapport and comfort with her on a "friendly" level to have her be interested enough to go out with me?