Some of mine: 'avoid like the plague' 'Suddenly' – if it happened suddenly, then don't delay it with this over-used adverb, just write what happened. 'His [insert human organ here] sank in his chest' – although this is a good description of what it feels like to feel a sudden shock of emotion, I usually try to come up with a more original description. 'It was a [insert weather adjective here] and [insert another here] night / day.' – this might have been an original opening three thousand years ago. Calling characters something that is blatantly descriptive of their character – not like the subtlety of Lord Voldemort, but more along the lines of 'General Grievous' from Star Wars.