The best advice I ever received about writing was in a beginning English class in college. The teacher assigned the students to write something like one hundred words per day in a journal or diary form and to turn these in once a week, mainly to show that they had been keeping up with the assignment. They could write about any subject or subjects they chose. There didn't have to be any thesis or any consistency; they just had to write a small quota of words each and every day. Over the years I have tried to continue to do that-- although I have had lapses. I must have written at least a million words--possibly two million. I haven't kept most of them. Writing has become fairly easy for me by now, although I would like to keep improving. Writing will become a habit if you do it regularly, producing a small quota every day. (If you are even a mediocre typist, you can write a hundred words in two minutes.) It will even become a necessity. By that time you will be a real writer. And you will find out a lot of things about yourself. It is helpful to read what you have written. You can see what sounds bad and what sounds good. You can rewrite some of the things that sound bad and make them sound better to your own ears. You can learn to deal with all the minor problems of writing such as punctuation, capitalization, and spelling. Ernest Hemingway was one of the greatest American writers. He said that he tried to write just "one true sentence" and then follow it with another true sentence. I have heard that he only wrote a few hundred words a day.
The way I write now is to turn out a first draft fairly quickly and then go back and read it to see if it makes sense and if it reads smoothly, so that a reader would not stumble over an awkward expression. I also want to make sure I didn't make any obvious mistakes. If necessary I write a third draft. Somebody once said that good writing is rewriting. But you don't need to worry about the first draft being perfect. James Thurber, an excellent writer, said: "Don't get it right, get it written." In other words, get something down on paper. You are not carving the letters in stone. They can always be changed. With time you will find that fewer changes are needed. But i don't think there's any way of becoming good at anything unless you do a lot of it.
The best book on writing I have ever found was the now-famous The Elements of Style of Strunk and White. E. B. White, who revised and expanded the original book by Wilfred Strunk, was one of the best American writers. He is now mainly remembered for his children's books Charlotte's Web and Stuart Little.