Here's a tactic I think has some promise....
Once you're well into into a conversation with a girl, produce a set of card and say "Pick a card, any card." When she asks what to do with it, say "Go ahead and keep it, I've got 51 left. (cribbed from Groucho Marx, but that's OK)" if she laughs, say "Or, write your number on it, shuffle it into the deck, and I'll see if I can find it."
Keep in mind that this idea just occured to me, I don't know if it will work or not.
Once you're well into into a conversation with a girl, produce a set of card and say "Pick a card, any card." When she asks what to do with it, say "Go ahead and keep it, I've got 51 left. (cribbed from Groucho Marx, but that's OK)" if she laughs, say "Or, write your number on it, shuffle it into the deck, and I'll see if I can find it."
Keep in mind that this idea just occured to me, I don't know if it will work or not.