Don’t make common grammatical errors.
There are lots of excellent writers who are poor grammarians. You may be one of those. But the editors you submit manuscripts to will probably never get far enough to know. Poor grammar or spelling will stop them before they find out how wonderful your manuscript is.
A synonym for a good writer is wordsmith. Does that word apply to you? Don’t submit an article until it does.
The term implies you are:
• Good with the writing craft, arranging your words (editors help with this all the time, but the less work your manuscript will be the more chance you have of getting it accepted)
• Good with grammar and spelling (get a good book and learn it). I have taught master's level courses and had students with terrible grammar.
Grammar and spelling are building blocks of the writing craft.