Verbs has to agree with their antecedents. Employ the vernacular. Foreign words and phrases are not apropos. Contractions aren't necessary. One should never generalize.
Comparisons are as bad as cliches.
Be more or less specific. Exaggeration is a billion times worse than understatement. Analogies in writing are like feathers on a snake. Go around the barn at high noon to avoid colloquialisms. Even if a mixed metaphor sings, it should be derailed.