My secret is that I only do it with people whose musical taste reminds me of either myself or someone I know. Then I zero in on precisely what it is about that person I know (or myself) that makes me like those bands, and extrapolate on that.
For instance, you listen to ISIS, Tool, A Perfect Circle, and Lacuna Coil, so you like really intense/distorted rock (hence secret desire to mosh), but you also listen to Trans-Siberian Orchestra and Porcupine Tree (which screams "nerd," and therefore, "probably physically fragile" and "not friends with lots of girls but good friends with a few"). The part about the paranoia/annoyance regarding weed comes from the fact that you DON'T listen to music with a heavy bottom end or a heavy psychedelic influence, which you inevitably would by now if you liked getting high.
I draw all these conclusions from comparing you to myself, a friend I had in the first couple years of college, and guys who wear shirts with prog-rock bands on them (you are not one of them, they are usually bigger than you and have long hair and possibly neckbeards). At least one or two of your friends in high school probably have/had bad acne and probably wear/wore button-down shirts with airbrushed artwork of dragons (or maybe even anime characters) on them. Those are the ones now wearing prog-rock t-shirts, and you went a different direction and you probably wear dark solid colors almost exclusively.