Whether people read as a hobby or not. As it implies a type of interest into the world around them.

And as a lesser second, what they read.

Disheveled hair. If you have long(ish) hair and you're going out in public, at least drag a comb through it so you don't look like a bed-head.

Their taste in music. Sorry but if Pink Floyd is your favorite band i have to assume you're boring

For being british.

Eating meat although they're fully aware, that we have to shift completely away of that (GHG emissions, land-use), and then blame the government that they need to regulate this more.

Yes more government regulations would be great, but it's one of the few individual things that have effect, if everyone would think similar. And a vegan or mostly vegan diet is not really worse in taste and likely more healthy as well... Eating meat is not sustainable (nor morally justifieable), it should be a thing of the past...

If I told you, it wouldn't be secret.

Why yes I am a clever little scamp!