1. Preparation is the key
Do all of your research first, before you start to write. Even a letter normally requires some minor research such as making some phone calls or reviewing a file. It's also very important to prepare yourself mentally before writing. So don't sit down to write too soon. Mull it over for a while, sometimes a day or two, sometimes an hour or two, depending on the complexity of the job at hand. It's amazing how the sub-conscious mind will work on the problem 'behind the scenes' and when you finally do start writing, it will flow.
2. Always use a sample
For me, this is critical. No matter what I write, it helps tremendously if I have some visual stimulation. If I'm writing a letter I post a copy of a similar letter, or the one I'm responding to, somewhere in my direct line-of-sight. It helps me focus and keeps my mind on the subject at hand, minimising the tendency for my mind to wander. No matter what it is, I always make a point to find some previous work or a sample of work similar to what I'm doing. It really stimulates the creative writing process and increases productivity significantly.
3. Shorter is always better
Whether you're writing a report or a letter, look for ways to cut it down in length. Concentrate on conveying the essential message. If something you've written does not enhance the core message, or doesn't add value, consider cutting it. These days, you have to be 'short and to the point' to get your message read.
4. Use concise and appropriate language
Your letter or report should use simple, straightforward language, for clarity and precision. Use short sentences and don't let paragraphs exceed three or four sentences. As much as possible, use language and terminology familiar to the intended recipient. Do not use technical terms and acronyms without explaining them, unless you are certain that the addressee is familiar with them.
5. 'Be' your addressee
A key technique to use when writing anything is to clearly 'visualise' your audience. As you write, try to imagine in your mind's eye the specific person(s) to whom your written product is directed. I often imagine that I am sitting across the boardroom table from my addressee, trying to explain my points in person. Make an effort to see the situation from the other person's perspective. What would you be looking to see if you were the recipient of the letter or report?
6. Do the outline first
Even if it's a one-page letter, it doesn't hurt to jot down a few quick notes on the main points that you want to cover. This process forces you to think logically about exactly what you want to cover and it helps you decide in which order you will approach your subject. For a letter this is helpful. For a report, this is absolutely essential. In fact, I believe that you should force yourself to go through the entire thinking process that is required to develop a complete draft Table of Contents, before you start to write any report.
7. Write and then rewrite
No matter how much preparation I do, I always find that I can improve on the first draft. That's partly because when I'm writing that first version, my main focus is to get the essence of my thoughts down on paper. At that stage I don't worry about perfect phrasing, grammar or logic. My main mission the first time through is to make sure that I capture the critical words and phrases that form the core meaning of what I want to communicate.
8. Format is important
Whatever you are writing, make sure it looks professional. This is where proper formatting comes in. Your credibility and/or that of your organisation is on the line, with your report or letter serving as your representative. If it is not professionally formatted, it will reflect negatively on you, even if the content is good and it is well-written. Rightly or wrongly, the value of your work will diminish in people's eyes if the formatting of your document is shoddy or amateurish looking.
During my 25 year career in a variety of professional positions in both the private and public sectors, I have written literally thousands of letters and memos and hundreds of reports. If I had to boil down everything I've learned about practical day-to-day writing for both personal and business purposes into 10 key points, this would be my 'Top 10' list.
3. Shorter is always better
9. Read it out loud