Editors do not want Repeat-Subjects as a Rule
Avoid offering articles on subjects that have already been dealt with in a periodical. Unless you have unique and valuable information to add to that already given, space cannot be spared to repeat matter. Moreover, the public does not want to pay twice for the same thing—and that is what it would amount to.
It is no recommendation to write to an editor, "I see you have an article on 'Glow-worms as a Hat-Trimming' in your last issue; I am therefore sending you another article on the same subject." Unless you have some new and really informing data to contribute, the probability is that you would only be covering the same ground as the previous writer.
Neither are you likely to get your MS. accepted if you write, "I have read the article on 'Glow-worms' in your last issue, and disagree with many of the statements made therein. Far from glow-worms being things of elusive beauty and suggestive of fairyland, as your contributor calls them. I regard them as noxious pests. I have written my views in detail, and hope you will be able to publish the article in your next issue to counteract the wrong impression that the other one conveyed."
Now, an editor to a large extent identifies himself with the views expressed in the pages of the paper he edits. And had he not approved of the statements made, he would not have been inclined to print them in an ordinary non-controversial paper. Is it likely, then, that he would want another contribution calmly informing his readers that the previous article was entirely wrong and unreliable?
On The Subject of "How to——"
Most editors are overdone with the usual "How to—" articles. The public has by now been told "How to" do everything under the sun, I am inclined to think; but if you feel it laid upon your soul to impart still further instruction—try to find a fresh form of title.
Do not choose too big a subject. "Heaven," "Human Nature," "Eternity," and kindred themes are beyond the powers of any mortal—much less the beginner.
Get right away from hackneyed phrases and allusions. So many MSS. are peppered throughout with such expressions as "all sorts and conditions"; "common or garden"; "let us return to our muttons"; "tell it not in Gath"; "but we must not anticipate."
If you feel drawn to write an essay on "Friendship," it is not necessary to start with David and Jonathan; they have already been mentioned—more than once, in fact—in this connection. Neither is it desirable, when writing about Jerusalem to quote, "a city that is set on a hill cannot be hid."