Entrepreneur has a list of their tweleve most common writing mistakes. These mistakes are targetted to business style writing:

1. You use industry buzzwords that are hackneyed and phony.
2. You assume the reader knows the acronyms or identity of the people you mention.
3. You overuse CAPS and punctuation.
4. You compose overly complicated, overly abstract or flowery writing.
5. You mix single objects with plural pronouns or single subjects with plural verbs.
6. You make one of these common mix-ups. (i.e., between/among, less/fewer, then/than, etc.)
7. You make vague claims.
8. You slip into slang.
9. You use unprofessional-looking font.
10. You make frequent and immature spelling mistakes.
11. You use quotes incorrectly.
12. You start a sentence with a numeral.