Both academic and business writing share the need for a purpose--that is, a reason the writing is undertaken, and a goal the writer wishes to achieve. In academia, this usually begins with an instructor's prompt; in business, this is often an assigned task or a need to present work-related information to others. Without a purpose, writing is a wasted task.
In any writing situation, planning is essential. The worst way to begin a writing project is by sitting in front of a blank word processing document, trying to write. Good pre-writing habits include background research, data collection, brainstorming and outlining--the goal is to do as much of the work as possible before committing to a single sentence in the draft. A good writer does not begin writing until he knows what he wants to say and how he wants to say it.
In both academic and business writing, the writer must give some consideration to their audience and adjust the message accordingly. Who will be reading the finished writing? What are their expectations? What do they already know? What do they *need* to know? By asking and answering these questions, the writer will help herself frame the message before drafting, and assist herself in the process of revision.
In both academic and business writing, a clear, readable style is preferred over a wordy, indirect approach. To achieve this, writers should choose concise words, use the active voice rather than the passive voice and avoid informality (such as contractions, slang and excessive use of exclamation points). Tone is also important--that is, what attitude or emotion am I expressing through my choice of words?
No matter the writing situation, it is important to follow the rules of standard written English. Grammar, punctuation and spelling should always be correct. Vocabulary should be as standard as possible, avoiding slang (though not jargon, if it relates to the subject). Citation, if required, should correctly and consistently follow an existing citation form, such as APA or MLA.