
Audience
The audience of a piece of writing should be the single most important factor you bear in mind when determining how and what you will say – especially in business. When you plan to send out a letter, memo, or other type of written message, consider who will be reading it and why. The underlying purpose of almost all writing is to communicate a specific idea or set of ideas through words. If you forget who will be on the receiving end of the writing, these ideas are much more likely to get skewed or misinterpreted.
For example, starting off a business memo with a personal message is generally not appropriate. Likewise, the legal jargon you might work with on a daily basis might not be best suited for an email to your grandmother.
Although written communication should always be tailored to your audience, your own personal writing style is an important part of making your writing effective. If you typically write brief, matter-of-fact memos because that is your personal style, there is no reason why you should be forced to adopt a more flowery style. In fact, switching from one style to another can actually create more problems, since your audience may read more into the sudden change than they would if you had remained consistent.
Formality
The level of formality of a piece of writing conveys much about the author (and the recipient). For business writing, using a formal tone, maintaining proper headings, and following specified formatting not only demonstrates your own level of ability and professionalism, but it also gives a clue as to how you perceive your audience. For example, a hastily written email condemning the practice of gossip at the water cooler does not demonstrate that either: a) you are taking the issue seriously; or b) you consider the email's recipients worthy of a more formal request. This type of email will most likely NOT result in your desired action.
Although you may not have the greatest writing skills in the world, there is no reason why you should be afraid of writing. Instead, you should write with your own skill level in mind. If you aren't the greatest at crafting lengthy sentences or using large words, don't. There is nothing wrong with using concise sentences – as long as you are using them appropriately.
Consider the following message:
All members of the executive-level staff must report to the conference room at precisely twelve o'clock noon on the anniversary of the organization's opening date.
This lengthy sentence has great potential for error. Misuse of hyphens, apostrophes, grammar, and spelling can easily occur among even the most experienced of writers.
This example would also work:
Will all the executive staff members please meet for our opening anniversary? We will be meeting in the conference room at noon.
Although you might prefer to use the first example due to the higher level of professionalism it presents, it is always better to err on the side of caution. Unless you are 100 percent certain of your skills as a writer, simple and correct is always better than complicated and potentially incorrect.

Written communication is much more permanent than verbal or nonverbal communication. When you write something down – whether it's on paper, email, or a napkin you found at a bar – there is no taking it back. This is why legally binding contracts are almost always restricted to writing: it's the one place where you cannot pretend that you "said" something other than what's there. This is why you should always write with the knowledge that the words you choose today can have repercussions in the future.