My best advice in picking a kitten is to bring home one that is very interested in you. For instance, when you take him/her into the bonding room, they want to sit around you, sniff you, figure you out, play with you, have you pet them, etc. Getting a kitty that ignores you as a kitten will most likely result in quite the aloof cat as they grow older.
Our babies were two out of a litter of four. I picked them (well, THEY picked ME is more like it) because Sunny (our little female) was VERY interested in the people around her, and was very social. (We brought Hobbes home originally because he and Sunny are so incredibly close, we didn't want to separate the two...but I've totally fallen in love with Hobbes now.) The other two in the litter consisted of one that TOTALLY wasn't interested or noticing the humans around her, and one that was VERY complainy. Needless to say, Sunny & Hobbes definitely fit the bill!
Sunny is definitely one of the sweetest cats I've ever had, and I've always made sure (when I had the choice) to bring home a really social cat that was interested in having (if not flat out needed) time with me/us. I wanted BABIES, not aloof, independant friends. Ya know?
Anyway, that's my best advice.
Hope it helps!
Oh, P.S. I was there when our babies were being born, and brought them home at about four weeks, and their personalities were already very much as they still are.
I do have to agree, however, that males tend to get much cuddlier after they're neutered, and females tend to favor more alone time after spaying. So if you find a female that is an absolute cuddle-bug, chances are she'll still want to be lappy when she's spayed.
Another thing, you might want to try multiple visits with the kitten in the room, since it might have just been more interested in the room itself at the time, and if it gets used to it, it might be more interested in YOU next time.