Speaking personally, I observe my perceptions of a person when I meet them the first time. I pay close attention to my iNtuition - it is seldom incorrect. My biggest problems in life have been when I have not paid attention to an 'inexplicably bad feeling' about somebody that I couldn't have explained. The other aspect is do we "speak the same language" - ie communicate well, have similar interests and approach to life. Of my small group of friends most are INTJ males, and one female.
I think we have feelings (gee, that is a real NT thing to say...) I do get passionate about things/issues/people. Geekishly so about issues/things. But when it comes to people I know I don't do the outward expression until I know them quite well. Yep, I've been called aloof, snobby or cold. But folks who take the time to get to know me know there is something much warmer under the surface. And those who know me well see my feelings in the subtle things like fleeting facial expressions/body language. NF/SF folks I know tend to wear their hearts on their sleeves and have their brains on "loud speaker".