There are five guidelines for writing formal prose. what should a formal prose writer avoid doing

The tone is the attitude of the writer. Two factors that greatly affect the tone are audience and purpose. The audience of an essay is anyone who might read it. An important factor in determining your tone is your audience. To figure out your audience, ask yourself, 'Who will read my essay?' If your essay is for a grade in class, then your audience is your teacher or professor. If you are writing an essay to be published in a periodical, your audience is anyone who might read that periodical. It is very important to know your audience because you will craft your essay for a specific audience. A final factor in setting the right tone is to determine the purpose of the essay. An author's purpose is the reason for writing. There are three main types of author's purpose: to persuade, to inform or to entertain. If you are trying to convince your reader to believe or to do something, then you are persuading. A purpose to inform means your goal is to give information and to teach your audience. Finally, to entertain means to amuse and be interesting to your audience. Besides these three main ones, there are many other types of purpose for an essay, like to describe and to express.

Hope this helps.