For all writers the most important people are their readers. If you keep your readers in mind when you write, it will help you use the right tone, appropriate language and include the right amount of detail.
What do readers want from writing? They want relevant information, presented in a clear, easy-to-understand style. They don't want muddled thinking, background information they already know, business-speak and jargon or waffle. Above all, they want to get the gist of your message in one reading—they don’t want to dig for the meaning through long sentences and a boring style. So if you always keep your readers in mind, you will have to adapt your style and content to meet their needs.
Getting a clear picture of your readers before you start to write helps to focus your writing to get your message across. The better picture you have of your readers, the better you can direct your writing.
Ask questions to get a clear picture of your readers.
Who are my readers?
What do they already know about the subject?
What do they need to know?
Will they understand technical terms?
What information do they want?
What do I want them to do?
What interests or motivates them?
What prejudices do they have?
What worries or reassures them?
What will persuade them to my view?
What other arguments do I need to present?
How are they likely to react to what I say?
If you imagine yourself in your reader's position, you're more likely to write a good letter.