I have learned from experience that you shock people when...
1. You wear purple eye shadow and a red top. I almost sent a make up woman on a film set into cardiac arrest once when I turned up with purple eye shadow and a red top. Ready for my close up? She thought not.
2. You tell people that you don't drink alcohol. I don't know what the experience of other non drinkers out there has been, but anytime I've told someone I don't drink alcohol they seem to take it as either a personal insult to their way of life or a challenge to make me drink before the night is through - or both. The look on their faces is almost akin to telling them I eat human flesh with fava beans for breakfast (minus the nice Chianti of course).
3. You pick the vegetarian choice on a menu. Ok, I'm not vegetarian but both knowing them and being mistaken for them has led me to realise that admitting to being one in public is almost as bad as saying you don't drink alcohol. Invariably when someone confesses to being vegetarian the meat heads in company will list all the animals they have eaten and how delicious they were.
4. You tell people you write horror fiction. Ok, maybe this one only applies to me. I've been called a dark horse when I told one person what I did. I'm not sure what horror writers look like, but maybe the goth look would be what people expect.