Just like a CSI investigator, you can frequently spot errors in writings if you can forget that you are the author and examine the work like a detective. Here are some of the most frequent suspects:

1. Missing comma after an introductory element
2. Vague pronoun reference
3. Missing comma in a compound sentence
4. Wrong word
5. Missing comma(s) with a nonrestrictive element
6. Wrong or missing verb ending
7. Wrong or missing preposition
8. Comma splice
9. Missing or misplaced possessive apostrophe
10. Unnecessary shift in tense
11. Unnecessary shift in pronoun
12. Sentence fragment
13. Wrong tense or verb form
14. Lack of subject-agreement
15. Missing comma in a series
16. Lack of agreement between pronoun and antecedent
17. Unnecessary comma(s) with a restrictive element
18. Fused sentence
19. Misplaced or dangling modifier
20. Its/It’s confusion

(Bedford-St.Martin’s Press)

Source:  http://www.bedfordstmartins.com/lunsford/twenty.html