Don’t send enclosures in a letter written by some one else; only the greatest intimacy can excuse this practice. Write your own letters and send in a separate envelope.
Don’t write a letter in a towering passion; you would not care to have it confront you in some cooler moment.
Don’t cross the writing in your letters. Life is too short and the time and eyesight of your correspondent too precious for this.
Don’t fill up every available blank space and margin of your letter with forgotten messages. If these are very valuable, add an extra sheet to your letter, thus saving its appearance and the patience of its recipient.
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.