1. Comma splice:  a comma used in place of a period or semicolon.

2. Run-on sentence: nothing used where a period or semicolon should go.

3. Sentence fragment.

4. Missing comma
            a) Comma not used before a co-ordinating conjunction joining two independent clauses.
            b) Comma not used to signal the beginning or end of a parenthetical expression.
            c) Comma not used to signal the end of an extended introductory phrase or clause.

5. Dangling modifier. Check your handbook.

6. Faulty pronoun agreement.

7. Faulty subject/verb agreement.

8. Misspelling. You may need some coaching on how to use your spell checker.  But also be sure to read your paper three times before handing it in. Technology can only assist.

9. Unintroduced quotations. Quotations cannot stand on their own. They must be introduced.

a) If introduced by a full sentence, that sentence should end in a colon.
b) If introduced by an incomplete sentence, that phrase should end with a comma.
c) If the quotation is integrated grammatically into a sentence, no special punctuation beyond the quotation marks is necessary.

10. Inappropriate or shifting verb tense. Use present tense unless past is necessary. In either case, be consistent. 

11. Undefined key term(s).

12. Overused parentheses or dashes.

13. Missing or misused apostrophe.

14. Missing or awkward transition.

15. Sexist language.

16. Doubtfully correct use of a word.

17. Non-existent word.

18. Clichés and slang terms.

19. Awkward word usage.

20. Failure to give references. What is the page number of the story or line number of the poem?