Foreign words and phrases are not apropos. Watch out for irregular verbs that have creeped into our language. Steer clear of quotations. Metaphors are like similes. Be more or less specific.
Understatement is always the best.
Exaggeration is a billion times worse. The passive voice is to be avoided. Use colloquialisms when pigs fly. Even if a mixed metaphor sings, it should be derailed. Above all, writing should be sincere, whether you mean it or not.