Vary your sentence structure - Nothing seems more unsophisticated than an uninterrupted succession of subject-verb constructions. Take a series of sentences like the following as an example: "Moby Dick can symbolize both a manifestation of God or of the ultimate evil.". Here are just a few of the variations you can make:
Melville renders Moby Dick as simultaneously a manifestation of God and as a symbol of the ultimate evil.
That Moby Dick is subject to a dichotomy of interpretations is evident in his depiction as both a manifestation of God and of the ultimate evil.
We may intimate that Moby Dick is a juxtaposition of both the divine and the diabolical.
Combine short sentences - Try reading your paper out loud. If it seems choppy it can likely be remedied by your grouping short sentences into longer, more complex ones. For example:
"Gatsby's obsession with Daisy has deeper implications. He becomes obsessed with escaping his own past."
This would be much stronger if combined:
"Gatsby's obsession with Daisy eventually translates into a yearning to escape his own past."
Don't use passive voice - Plain and simple. It makes your writing weak.
Bad: "This fact was proven by Napoleon's subsequent actions."
Good: "Napoleon proved this fact through his subsequent actions." The object of the sentence should never be turned into the subject.
Maintain consistency in tense - Don't drift from the present to the past to the conditional (from "he is" to "he was" to "he would have").
Starting a sentence with "there are" or "there were".
Using the phrase "this shows" (as a substitute say "evident in this fact is" or "This interpretation belies the idea that").
Using the word "quotation" when incorporating a direct quote. This makes for an awkward break from your natural thoughts, and creates an aura of self-consciousness in your writing.
The first person or second person tense. Sometimes using the first person plural (as in the previous example of "we may intimate") is generally acceptable, in that it conveys a universality that the "I" or "you" voices preclude.
Confusing commas and semi-colons. A semi-colon can be used to connect two short, related sentences into a longer one: "Trench warfare became standard during World War One; it was used in all the major confrontations.". A comma cannot be used in this way.
Confusing "who" and "whom"; the former is a subject, the latter an object.
Broad, non-specific words like "good," "bad," "nice," "important," "vivid," and "thing". If those are the only words you can use to express what you're saying, it's likely not subtle enough to make for a very good argument.
Next: Lesson Seven: Conclusion