how can you tell if someone is a P or a J? it would help me, thank you!

Sure, I tend to look at body language a lot: Js tend to carry more tension through their necks and shoulders, especially, but everywhere else too.  They tend to have better posture – Ps like to slouch.  Facially, Ps and Js smile pretty differently, too – Js smile from the corners of their mouths; Ps tend to go cheeks and eyes.

Clothing and hair is sometimes helpful – are they very neatly presented, or are they going for artfully messy or unconventional?

What top three types would u put with a pretty extroverted INTP?

I would put the INTP with the other INTPs, because that’s how this blog rolls.

Romantically speaking (I assume that’s what you’re really asking), in no particular order INTP men seem to marry mostly ENFPs, ESFPs, ENFJs and ENTJs.  At least, the famous ones, anyway.  I guess there’s also ISTJ – Michelle Pfeiffer who married David E. Kelley.

I’m not sure if it works the same way with INTP women or not.  Not enough data.

How do you differentiate between INFPs and ISFPs? :)

Again, good question.  I am still figuring it out. 

I am mostly mapping people onto other people and don’t do a whole lot of “Is this person an S or an N?” unless I run into people who don’t fit.

If I have to ‘S or N?’ them, the typing is usually pretty tentative until I can find a couple more people like them to solidify the typing – and usually at least one person in the group will not really fit S or N very well.

I wrote a post sort of answering your question a while back: http://mbti-sorted.tumblr.com/post/108317108048/what-are-the-main-differences-between-infp-and and it’s a little more concrete, but I’m not sure that I entirely agree anymore.