Final answer:
When writing in a formal tone, avoid using slang or informal language and contractions to maintain professionalism. Ensure clarity by using words correctly and adhering to proper grammar and punctuation.
Step-by-step explanation:
In a formal tone of writing, particularly in academic or business contexts, it is important to maintain a style that is professional and appropriate for the audience. To achieve this, two key things to avoid are: using slang or informal language, which can come across as unprofessional or too casual, and using contractions, which can make the writing seem less formal. Merely having complex vocabulary does not constitute a formal tone if the words are not used precisely. Moreover, accurate use of proper grammar and punctuation is essential and contributes positively to the formal tone. It is crucial to ensure clear communication by choosing words you understand fully and using them in their correct context.