The document discusses common writing mistakes such as misusing articles, lacking transitional phrases, and improperly using adjectives. It also addresses issues with switching verb tenses unnecessarily within a sentence, as well as incorrect capitalization such as not capitalizing the letter "I" or capitalizing common nouns. The key is to establish a consistent tense, only change tenses when appropriate like with time shifts, and pay attention to verb tenses and capitalization rules for proper nouns versus common nouns.