Verbs has to agree with their subjects. Avoid unnecessary redundancy. A writer mustn't shift your point of view. Don't write a run-on sentence you've got to punctuate it. A preposition isn't a good thing to end a sentence with.
Comparisons are as bad as clichis.
Do not use a foreign term when there is an adequate English quid pro quo. If you must use a foreign term, it is de rigor to spell it correctly. Avoid colloquial stuff. It behooves the writer to avoid archiac expressions. Mixed metaphors are a pain in the ass and ought to be thrown out the window.