Lengthy plot summaries and paraphrases. Summaries are great for…summaries.  When you’re writing an essay, you’re expected to argue towards your thesis – that means, an original use of various ideas.

Generic cliches. Cliches sound bad in any form – movies, novels, speeches.  Avoid them in your essays, at all costs.

Too many quotations. Quoting too much text from other sources (no matter how authoritative) means avoiding any original writing.  That’s it – bad grade for you.

Poor grammar and sentence structures. No matter how solid your ideas, no one will understand them if you write poorly.  Use a grammar checker to give your thesis a chance.

Padded writing. Longer does not necessarily mean better.  If you think you’ll get extra points for padding sentences with redundant statements, you’re kidding yourself.  Concise writing demonstrates more hard work than an unnecessarily long one.

Too much facts, not enough discussion. Facts are always necessary in good, well-written essays.  However, putting them in without due analysis makes them no better than eye candy.  Express an original opinion based on them and watch that grade improve.