A clean cauldron keeps potions from becoming poisons and antidotes are anti-don'ts unless approved by a qualified healer.
You don't seem to need many qualifications to liaise with Muggles; all they want is an OWL in Muggle Studies. ''Much more important is your enthusiasm, patience and a good sense of fun.'' - ''You'd need more than a good sense of fun to liaise with my uncle'', said Harry darkly .''Good sense of when to duck more like.
What she did have were Bertie Bott's Every Flavor Beans, Drooble's Best Blowing Gum, Chocolate Frogs, Pumpkin Pasties, Cauldron Cakes, Licorice Wands, and a number of other strange things Harry had never seen in his life.
Professor, Harry said, approaching the little Charms master, Professor, I'm sorry to interrupt, but this is important. Have you got any idea where the diadem of Ravenclaw is?
She is an immensely controlling person, and all who challenge her authority and world-view must, in her opinion, be punished. She actively enjoys subjugating and humiliating others, and except in their declared allegiances, there is little to choose between her and Bellatrix Lestrange.
We're with you whatever happens, said Ron.