This is one I've used a couple times on the phone and seen some interesting results. It's a little rough around the edges and goes contrary to the whole not showing interest mindset. However, I believe with some honing it could turn into a really awesome routine. Do you think it's good? Bad? Tear it apart! Field test it!

The trick is to never say "sweetheart" until you've built up some rapport and are getting ready to end a conversation.

You: "...Well, I'll talk to ya later sweetheart" (say this like it just slipped out)

Her: "Did you just call me sweetheart?" or "You called me sweetheart"

You: "Oh, I did?" (Play dumb)

Her: "Yeah, I liked it"

You: "Oh, you did?" (Again, play dumb)

Her: "Yeah, I really liked it" (she'll emphasize this heavily and start to get kind of mushy on ya)

You: "No one has ever called you sweetheart?"

Her: "No" or "Yes" (Doesn't matter, if she says Yes possible neg?)

You: "Well, don't get used to it. I only call girls I like that. Got it sweetheart?" (Push/pull)

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I have foudn that girls are very reluctant ad directly admitting htey like something so I think that part of this routine will be invalid in some if not most cases