My boss tells me I should be able to write a letter or a report on something even if I don't know the subject that well. I used to call that BS when I was young, but maybe he has a point.
I wrote the article The Art of Minute Taking and I had only taken minutes a few times about 25 years ago. How did I do it? I interviewed my friend who is a minute taker. I asked her questions to prompt her and got her talking about minute taking while I took notes. At the end of it, I knew how to take minutes and could write about it. From writing that article I had confidence to take a job that required me taking minutes and it has turned out fine. What used to scare me, has now become something I can do. I will not say I am the perfect minute taker, but it is something I now have confidence in doing.
I have written many articles on my blog on subjects that I knew nothing about. I did do research however and read as many articles and books on the subject that I could and then I tackled the article and actually learned something while doing it. Writing on a subject you know nothing about is a good way to learn something about that particular topic. Being able to do that becomes helpful when you need to know the information for your job or some life experience. For instance, at one time I would not have been able to write about cystic fibrosis, but since my great nephew has been diagnosed with it, I have learned more than I ever wanted to know and yes, I could write an article about it.
I still have difficulty writing flowery letters with all the added fluff that I don't know about, but I am learning and in the end it does make the letter sound better.
A good way to learn letter writing and style is from someone who knows how to do it well. Read their letters and reports and see how they craft their words. There is usually a pattern. The opening is typically a general who you are statement. You then proceed into the purpose you are writing and what you need from them or want to tell them. You then want to end with something to tidy the letter up and end on a cordial note and let them know you appreciate the time it took them to read the letter.
I think once you learn the pattern it is simply a matter of filling in the blanks, but then again, I've just written an article that I know nothing about. See, it wasn't that hard after all now was it?