He was at a wedding not long ago, and a young twentysomething woman came up to him and said, "Nice tie."
"I realized," he told me, "that she was hitting on me. I mean, honestly, a woman saying to a man, 'Nice tie,' can't be anything but a pickup line. It's like saying 'Nice ass' or 'Nice package.'"
After I stopped laughing loudly at that nugget of wisdom, I mentally jotted this down in my imaginary self-help book, Jane's Guide to Picking Up Dudes:
#78: Tell him, "Nice tie."
That, coupled with a slight smile, oughta do it.