He starts making a list. "It's good Slytherin behaviour to have inscrutable goals; it's Proper Slytherin Behaviour to have very clear and obviously correct public goals that are not in fact your real goals. It's good Slytherin behaviour to technically-not-break-rules; it's Proper Slytherin Behaviour to not be found out while doing that; it's Extra Proper Slytherin Behaviour to be the one making the rules. It's good Slytherin behaviour to know your enemies better than your friends; it's Proper Slytherin Behaviour to never let other people think of you as their enemy no matter what you think of them." He shrugs. "There was more, but at some point I had to pay more attention to holding my giggles than to listening because this is the House that supported a Dark Lord and thinks muggles aren't people. Most of them couldn't recognise a cunning plot if it danced on the table and threw its bra at them."