Related:

• Keep your ear to the grindstone, your nose to the ground, take the bull by the horns of a dilemma, and stop mixing your metaphors.
  -- Grammar rules for the unenlightened...
• William Safire's Rules for Writers: Remember to never split an infinitive.
  The passive voice should never be used. Do not put statements in the negative form....
• Mixed metaphors are a pain in the ass and ought to be thrown out the window. -- Writing Rule 27
• Avoid tumbling off the cliff of triteness into the black abyss of overused metaphors.
  -- Grammar rules for the unenlightened...
• Some people take the bull by the horns--others shoot it.
• You ought to take the bull between the legs.
• Metaphors be with you!