Much has been written about how to become a good English writer, with just as many answers provided. Through all the years, however, the essence of the responses tend to remain the same: you need to put in the hours of practice necessary.
If you've ever read the book Outliers, the single point emphasized over and over during the first half of the work is the fact that you will need to practice in order to reach your true potential. Geniuses may be born every minute, but few of them ever reach what they could be capable of, largely because they didn't put in the hours.
Are you hoping to become a professional writer someday? Take this advice to heart and follow it the best you can:
1. Be an avid reader. The more varied the materials you consume, the wider your appreciation of writing is going to be. If you wish to be a magazine writer, then read all sorts of prose written for that end, which includes everything from Rolling Stone to Martha Stewart. Don't be afraid to venture into literature, either - the more you expose yourself to, the greater the tools you are arming yourself with.
2. Write everyday. In the book Outliers, they demonstrated (albeit not very convincingly in some cases) that you need a minimum 10,000 hours of practice to reach a professional level of proficiency at any skill. So what are you waiting for? Start writing now.
3. Pay attention. Learn to pay attention to the moment. When you read materials, notice how they are presented such that they make perfect sense. When something confuses, notice the mistakes in it that lead to the muddled conclusion. If you can see, you can understand.
4. Work with text correcting software. Whether you employ a style checker or an all-in-one grammar software, these tools can help shape your proficiency in ways you can never do alone. It's too cheap an investment not to have at your disposal.
5. Enjoy the process. You won't become a good writer overnight. If you don't have the talent to begin with, you'll likely need at least 1,000 hours of practice to gain decent competency, let alone become good. You can either get from your starting point to that place of skilled ability begrudgingly or savor it. Learn to enjoy the process - you deserve to.