The thing that's helped me the most is the MuddyUm editorial staff. Most publications either accept or reject your work, but the MuddyUm editors provide good perspective on the content of articles. I've also learned to make it easy for them to help me. Try to keep articles to like 600-800 words, and I'm better at catching my own grammar mistakes. But, yeah join that MuddyUm Facebook group too and I'll meet you over there.