The following checklist is targeted at undergraduate students who find that they are able to construct in their minds strong and sophisticated arguments that bring together compelling and original ideas, but are unable in their writing to express these arguments and ideas clearly, accurately and effectively. The force of their arguments is thus severely diminished and they end up with poor grades that do not reflect the quality of their thinking. This is not to say that ‘writing’ itself should be thought of simply as a neutral medium to convey already complete arguments and ideas—the writing process fundamentally constitutes the formation of our thoughts. For practical purposes, though, it may be wise to try to isolate ‘problem areas’ in order to deal with them more systematically. Improvement will take time, but it can be speeded up with self-conscious practice and experimentation. Here are some of the areas to look out for when writing and editing typical argumentative essays:
Standard English   
    No grammatical errors (e.g. incomplete or awkwardly structured sentences, dangling modifiers, problems with subject-verb agreement, punctuation mistakes)
    No misused words -> Always check the dictionary
    No jargon or slang (meaningful only to a very specialised or local audience), unless:
        You explain what they mean
        You have good analytical or dramatic reasons for using them
    No typographical errors, e.g.: - Cut-and-Paste’ mistakes
        Spelling mistakes -> Use the spelling checker on your word-processor
Clarity    
    Effective choice of words -> Avoid ambiguity: Be specific and exact
    Effective placement of words in sentences to eliminate ambiguity
    Sentences are not cluttered with repetitive words, redundancies and inflated phrases
        Avoid clumsy sentences that confuse and irritate readers
    Systematic paragraphs convey ideas clearly, logically and purposefully
Consistency   
    Consistent use of verb tenses
    Consistent use of first-person, second-person and third-person pronouns to maintain the point of view appropriate to the contexts
    Consistent use of spelling, grammar and style conventions (e.g. British/American/Australian English, single/double quotations marks)
Tone   
    Sufficiently formal as appropriate to an academic essay
    No clichés and colloquialisms, unless you have good analytical or dramatic reasons for using them
Personal Style/Voice   
    No mimicking of lofty and pretentious styles or use of ‘big’ and excessive words in the vain attempt to impress readers
    A consistent style that you are comfortable with, because it reflects your own individual voice
    A variety of sentence structures used to avoid monotony
    The writing is not dull and lifeless, but elegant, clever, witty, energetic, etc.
    No sexist, stereotypical, or offensive language
Sense of Audience   
    Your interest in the topic is conveyed to your readers
        You must convince readers that they should also be interested in what you have to say
        It always helps to imagine yourself as the reader
    Actively engages the reader, e.g.:
        Well-paced writing: Short sentences to emphasise a point, long and complex sentences to slow down readers, etc.
        Suitably dramatic moments: Delaying information to make conclusions more satisfying, etc.
Formal Requirements   
    Falls within the prescribed word limit
    Complies with the prescribed format (e.g. fonts, margins, line spacing, justification, section headings)
    Consistent adherence to the prescribed style of documentation (e.g. APA, Harvard, MLA)
source: 
http://www.cdtl.nus.edu.sg/success/sl36.htm