This is a question we get a lot:
"So I'm definitely sure I'm an ENTJ now, what kind of person should I be looking for?"
It's a completely valid question, and I've read a bunch of great snippets about why it's important to find someone with the same last letter as you (J or P), how opposites attract, or how dangerous it can be to marry your shadow. But when it comes down to actual human relationships — and I mean in reality and not just in theory — I have to wonder if we're all asking the wrong question.
The idea that a certain type would work best with a certain other type assumes that everyone of a certain type is fairly uniform.
We already know this isn't true. No boxes here.
A few years ago, I had two INFJ roommate. Both were girls in their 20's. One is a pretty "classic" INFJ with her moody but loving Fe, inner Ni world, and photography-loving, candle-lighting, music-hoarding little baby Se. The other is still obviously an INFJ, but really, really likes her Ti. She can come across as very intellectual and logical. For an INFJ, she enjoys learning, understanding, and intelligent conversation a lot.
Both are definitely INFJ's, but they'll each look for completely different things in men.
So, what question should we be asking?
Who are your friends?
If anything's a good sign of who's compatible with you, it's the people you've already grown close to.
Are you an ESTJ guy who's best friend is an INTJ? That doesn't necessarily mean you should go looking for a hot INTJ girl, but it does give you some major insight. What are the things that you enjoy about your friend? What's kept your friendship solid over the years? I bet those qualities aren't what you've been looking for in a girl, but maybe they should be.
Go to Google and search "INTP ISFP Relationships". You'll see lots of people asking things like "I'm an ISFP and there's this really cute INTP..." and lots and lots of responses like, "No! Don't do it! Steer clear!!!" "The Fi...omg it's not worth it man..." "You guys don't have ANY of the same functions!" "Inferior Te drives me crazy..." "INTP's are emotionally retarded, don't you want someone who'll be able to connect with you?"
And you know what, in theory, they're totally right. I mean, come on. Look at it:
ISFP - Fi, Se, Ni, Te
INTP - Ti, Ne, Si, Fe
That looks like a recipe for poop cookies.
BUT... My best friend is an INTP, and I'm an ISFP.
In fact, he's the best friend I've ever had. I followed him to Ireland when he moved, am running a business with him, and our friendship is the easiest relationship in my life. Being with him doesn't cost me anything, and he says the same about me. We'd rather do things together than on our own 90% of the time, even as introverts, because being with each other is like being alone. (All the I's probably get the monumentality of this and the E's are scratching their heads; just bare with us extroverts.)
Not to mention we've known each other for 7+ years, and been roommates for 6 of those years. This isn't just a facebook friend, guys. This is a do-you-want-to-make-breakfast-or-should-I friend.
We just recently got married, but before we realized we were head over heels in love, I didn't think this meant that I should only "shop" for INTPs. But it definitely breaks down any thought of "I could never be with them." Why? Because I've discovered that everything I once thought I wanted or needed in a friend was wrong.
Because I looked at my friendships to see what "worked for me", I was getting to know more about what I like in general — I like Ne when it's used like this, but not like this, etc. — and that has helped me choose both a mate and future friends.
So, I ask you, who is in your life? Who's company do you enjoy the most? There's a lot you can learn about yourself and what "works for you" by studying those relationships.
[Edited to reflect Beck and I's relationship! - April 13th, 2017]