i have niche interests that for a certain amount of time/short phase am very interested in. Usually these accompany a joke that my friend group finds funny (ex I have a wall dedicated to Dwayne the rock Johnson, even though I don't really like him that much? I used to collect horse memorial every, idrk about horses? ) or a new friend/ crush (poetry, a tv show, an author, or something that I feel like brings us together). 

Question: 
But how do you know what you really like, and how do you stick with a set of things you like when getting to know a new friend? 

I'm not fake but if someone's like "I love Buffy the vampire slayer let's watch it," even though I haven't thought about it in years I'll be like, "hell yeah me too it's so good," even to the point of going to a Buffy Quizzo at the bar and realizing I actually don't know shit about it!!!