Never use a metaphor, simile or other figure of speech which you are used to seeing in print. Never use a long word where a short one will do. If it is possible to cut a word out, always cut it out. Never use the passive where you can use the active. Never use a foreign phrase, a scientific word or a jargon word if you can think of an everyday British equivalent. Break any of these rules sooner than say anything outright barbaric.