Twenty-five years ago, I bought The Art of Writing, a volume in the "Made Simple" series. It had been written ten years earlier and has an out-of-date feel now. So what? I feel out-of tune with the age too. Browsing through it again recently, I discovered many shortfalls, the worst being its lack of guidance on writing sentences.
You'd think that The Art of Building a House would have a chapter on bricklaying, or how to build the walls out of mud and wattle. But a book on laying bricks---or even making them---would not tell you how to build the whole house.
I have no idea how to write a book, though I have written one to someone else's order, which was not very satisfying. Long ago, I planned an erudite volume, to be called Seer and System, whilst commuting to work on London's Underground. All I had was ideas. I was defeated by structure and could not even write an attractive sentence.
I have since realised that my default style, the thing that comes naturally, is to start afresh every time and to stop after about 500 words. What seems natural is a little piece of prose that hands over to the reader's imagination very soon, after being painfully truthful about my experience---the only thing I know.
So blogging suits me perfectly. It's immediate, informal, small-scale.
In writing, every sentence can be a miniature work of art. I don't mean overwork it till you are bored, or till the reader thinks you are trying to be clever. Play with word order. The beginning of a sentence is one hotspot and the end is even hotter. Manipulate the word order to put the most significant part of your statement at the end.
Be aware of repetition, I mean use it to your advantage, as in a tune; but control any re-use of same word or phrase which jars the eye and ear.
Look at your writing critically, as soon as your sentence is complete; but also hours or days later.
Blogging is great: you get free critics.
I don't know if a writing course would truly help. Blogging is a training to write, and it could go on for life. But you need a good eye and ear, not to imitate the bad writing of others, and not to betray your own soul. You must be tuned to what delights you.
And then you have to work on delighting others too.