DH and I met through work, and the first thing I noticed, which Vorpal Bunny mentioned, was his politeness, especially to waiters and waitresses. I can't deal with rudeness "just because". I got to know him better and loved the way he listened to me so attentively, and of course I loved the way he treated both my pets and his. If you don't love animals, it's a no-go.
But the real clincher was we'd been officially dating only 3-4 months when my grandpa died. I had to fly back to Chicago and he offered to come with me. So he came and met the family, who loved him. But my grandma - I couldn't believe what he did. He came up to her at the pre-event (coffee and stuff before the funeral) and sort of bussed her on both cheeks in European fashion. He's a tall guy and he bent way down, took both her hands in his, said something quietly to her, and then did the bussing thing. I was watching her eyes while this went on, and she looked so utterly charmed by it.
It's kind of hard to explain how it came down and he almost sounds kind of pervy. But it was very comfortable and I will never, ever forget the look on her face. Somehow he penetrated her grief for a few minutes, and that's when *it* happened.