The president expects his staff to show up ready. As one senior aide told Politico's Amie Parnes, "If people aren't prepared, if ideas are half-baked, he gets a little annoyed because he feels like he could be using his time better."
He also dislikes when people monopolize the conversation at meetings, preventing others from speaking — and when people try to micromanage his time, another aide told Parnes. "If you spend too much time telling him where to go, how you get there, and everything in between, it drives him crazy."
Also worth noting: POTUS can't stand gum that comes in paper wrappers (only plastic-packed Dentyne Ice for him, according to a book by his former right-hand man, Reggie Love), and — Love learned this the hard way — he will not stand for candy in his trail mix.