Met at a party (late 20s) and was instantly attracted. Slim, athletic, carried himself well, amazing cheekbones and blue eyes. A fun one night stand, I thought, and he came back to mine that night.
First proper date was dinner at his. I can hear the squawks of horror from here... cheapskate, he just wanted sex etc. And we both lived in houseshares to boot so his housemates were all around too. But it completely sold me on him because it turned out he's an incredible cook. I still wasn't thinking in terms of a relationship at this point but the thought that if it worked out I'd eat well for the rest of my life did cross my mind.
Then I got to see everything else over the next few months. Extremely intelligent (but in a different direction to me so we complement each other without feeling inferior). So gentle and non-confrontational, the kind of man you instinctively feel safe with. Good ethics, good politics, lots of overlapping taste in music/film/books, as happy pottering round art galleries as playing sport with me. He got on with my friends, I got on with his. Neither of us wanted children or to do grown-up sensible settling down. We were both big partiers and while that's more medium-sized now, neither of us are the kind of person who retreats from having fun at age 30 because they're too old to go to clubs now.
Something incredibly key - when we met I partied a lot, travelled a lot, went clubbing a lot. He never tried to control that or to "tame" me. And neither of us did stereotypical gender socialising - he hates lad culture and his group of friends never deliberately hang out as "the lads" or "the girls", and neither did mine. So no trace of weirdness about my male friends, even former flings.
I actually knew he'd be a great long-term partner very soon, I think. It took me much longer for me to accept that's something I wanted for myself, and I'm happy I eventually did.