Express disgust for things that people love.
I recently chatted with an acquaintance who has been living and working in Boston for a couple of years. As we were catching up, I mentioned that I live in Provo and how much I enjoy living there. His instantaneous, visceral response?
"I hate Provo."
I wasn't particularly excited to continue the conversation at this point because the rather vehement expression of hate seemed tasteless and over the top.
"Well, thanks for dissing my home," I replied.
"Bah. Screw Provo."
If you'd like to perfect your ability to lose friends and alienate people, you'll really want to follow this model of conversation for a couple of reasons.
People dislike it when you assume their tastes are inferior to yours. People are partial to their own tastes, and insulting their preferences will make them feel defensive and create an environment of conflict.
Your unqualified expression of dislike turns the person's emotional investment in your friendship into a loss, not a return. They took a risk telling you something personal—something that makes them who they are—and you invalidated it. They are not likely to make future investments.
It is the epitome of narrow mindedness.
Empower your circumstances to govern your attitude.