Another line from an English movie. I try and avoid them, but some of them stake such a strong claim, that you cannot look away. This line is from the 1996 Tom Cruise - Renee Zellweger starrer, Jerry Maguire. Tom plays the eponymous role of Jerry, whereas Renee plays the role of his love interest Dorothy. The tag line of the movie was 'Everybody loved him...everybody disappeared'. In a competitive and cynical world, success is the only god and sports agent Jerry Maguire faces a lot of rough weather in his career. He has had a spat with Dorothy and Dorothy is with a support group of elderly and otherwise single women. They are all discussing how they hate men. And that is when Jerry walks in. He has had a big success in the face of a lot of adversity and feels empty as he is not able to share his success with someone he loves. He goes to the house where the support group is having a meeting, knocks and says 'hello...hello'. Then he goes on for 2 minutes and 47 seconds about how he is looking for his 'wife', how he would not allow her to get rid of him, how he wanted to share his success, how he felt incomplete without her, how he missed his 'wife' and so on. And then he says
"I love you, You...complete me...And I just...."
That's when Dorothy cuts in and says
"Shut up...shut up ...you had me at 'hello'"
The literal meaning of this is pretty obvious but figuratively can be used whenever you have agreed or accepted a proposal or suggestion from someone but the person goes on selling and persuading you. That's when you can say
"You had me at 'hello'
Whether you want to add the 'shut up' - now that I would leave to you.