If you wish to write well, you need help in understanding and avoiding the four types of mistakes: spelling, punctuation, grammar and usage. There are many types of writing mistakes as you will find out in this chapter. 1. Spelling mistakes. 2. Run-on sentences ( no commas before coordinating conjunction) 3. Sentence fragments 4. No comma after an introductory phrase 5. Wordiness? Verbose. 6. Comma splicing 7. Comma misuse (Inside a compound subject) 8. No commas around interrupters 9. Squinting modifiers 10. Subject-verb agreement.