Don't divide a syllable at the end of a line. The printer may do this, not the letter-writer.
Don't fall into the habit of using long words in a letter, they show a straining after effect. One should "say," rather than "observe," "talk," rather than "converse," if one's missives are to be easy, well-bred and readable.
Don't refold a letter, the marks always remain to show your carelessness. Fold it correctly the first time.
Do remember to answer all important questions in a letter clearly and decisively.
Do burn the great majority of your letters after answering. Those that are to be kept should be filed away in packages adding date and writer's name on corner of envelope and by a word or two suggesting the topics with which they deal. This will save time in referring to them.
Do answer your friendly letters with reasonable promptness. To do otherwise is a breach of etiquette. An unanswered letter is an insult, a cut direct. Business letters, of course, must be replied to at once.
Do send a postage stamp when you write a letter of inquiry, the answer to which is of interest only to yourself. A stamped and addressed envelope would be a still better enclosure.
Do, if you are an absent son or daughter, write home promptly and regularly; the comfort this will be to the parents at home, and the pain they suffer at any negligence on your part, cannot be overestimated. Husbands and wives, when separated for a time, would do well to follow this same advice.
Do date your letters carefully. Events and proofs of the greatest importance have hung upon the date of a single letter.
Do put sufficient stamps upon a letter to make sure of no extra postage falling to the lot of your correspondent.