It's a reoccurring pattern in my life. I'm invited to participate but nobody mentors me when I do. Mrs. Blacklock didn't disciple me after I gave my life to Christ at her vacation Bible school. VE6BOS had no time to "Elmer" me when I studied for my amateur radio exam. And freelance writers were too busy to coach me. Consequently, I wasted a lot of time, money, and effort trying to be a self-taught writer.
Twenty years of trial and error have taught me much. One important lesson is to find and join a writers' group. Members are more than willing to help novice scribes since they were once in that situation.
Reading writing magazines is another must for new writers. We all thought we were good when we began but in retrospect, we stunk. I still cringe when I open files from years ago and realize how poorly I wrote. So the price of those magazines proved to be a bargain after all since they taught me so much.
Self-publishing also gave me much to learn. Helpful editors not only pointed out my errors but explained why what I wrote was incorrect. Though they were busy, they did point me in the right direction.
Writing courses are also valuable to new writers. Instructors give relevant feedback and often correct our misconceptions on various writing styles.
The best advice I can give to beginners is that it isn't as easy as it looks. You need to listen to other writers and read guidelines thoroughly. Magazine and news paper editors are swamped with work and have no time to critique your submission. They often don't even bother to reply if your work is clearly wrong for their publication.
Don't be shy. Join a writing group for support and critique. Chances are that people will help you to write powerful and mistake-free prose or poetry. Persistence pays off in the end but you need others helping you to become skilled at the craft.