This is one ive only recently started using on girls my age.

Okay so what you should do is either:
*Start some sort of debate
*An argument
*Or make an observation

Now the trick is to be wrong in this situation(Or right if you feel you can pull it off)

Now when you are wrong, and it is aware to the girl that you are indeed wrong, tell her the simple line of ''Oh dang, ah well I guess I owe you lunch then''

Now try to follow up on that somehow (be persistent, otherwise i find that they think you're joking)

Ive used this line on about three girls, and it worked on two (havnt been arsed to follow up on three)

Try substituting the line supper for lunch, and say it more firmly. Remove the word guess.

This is hilarious. You know there is an episode of Seinfeld all about this?

I remember the first bet the guy made with Elaine was that Dustin Hoffman was in 'Star Wars'

It is a good one.

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"I've learned that people will forget what you said, people will forget what you did, but people will never forget how you made them feel"