How to write

1. Pronouns should follow the Nouns to which they refer, without the intervention of any other Noun.

Avoid, “John Smith, the son of Thomas Smith, who gave me this book,” unless Thomas Smith is the antecedent of “who”. Avoid also “John supplied Thomas with money: he (John) was very well off.”

When, however, one of two preceding nouns is decidedly superior to the other in emphasis, the more emphatic may be presumed to be the noun referred to by the pronoun, even though the noun of inferior emphasis intervenes. Thus: “At this moment the colonel came up, and took the place of the wounded general. He gave orders to halt.” Here “he” would naturally refer to colonel, though general intervenes. A conjunction will often show that a pronoun refers to the subject of the preceding sentence, and not to another intervening noun. “The sentinel at once took aim at the approaching soldier, and fired. He then retreated to give the alarm.”

It is better to use The Rule of Proximity.

2. Clauses that are grammatically connected should be kept as close together as possible. Avoid parentheses.

The introduction of parentheses violating this rule often produced serious ambiguity. There is an excessive complication in the following:–”It cannot, at all events, if the consideration demanded by a subject of such importance from any one professing to be a philosopher, be given, be denied that…”

A short parenthesis, or modifying clause, will not interfere with clearness, especially if antithesis he used, so as to show the connection between the different parts of the sentence, “A modern newspaper statement, though probably true, would be disregarded at if quoted in a book; but gossip is considered gospel.”

Here, to place “though probably true” at the beginning of the sentence would not add clearness, and would impair the emphasis of the contrast between “a modern newspaper statement” and “gossip.”

3. In conditional sentences, the antecedent or “if-clauses” must be kept distinct from the consequent clauses.

There is ambiguity in “The lesson intended to be taught by will be lost, if the plan of operations is laid down too definitely beforehand, and the affair degenerates into a mere review.” Begin, in any case, with the antecedent, “If the plan…” Next write, according to the meaning:

“If the plan is laid down, and the affair degenerates…then the lesson will be lost.”

Or

“… then the lesson … will be lost, and the affair degenerates into a mere review.”

4. Dependent clauses preceded by “that” should be kept distinct from those that are independent.

For example:

“He replied that he wished to help them, and intended to make preparations accordingly.”  Rather than “He replied …, and he intended.”

“Intended,” having no subject, must be supposed to be connected with the nearest preceding verb, in the same mood and tense, that has a subject (wished). It follows that is a condensation of: “He replied that he wished …, and that he intended.”

5. Where there are several infinitives, those that are dependent on the same word must be kept distinct from those that are not.

“He said that he wished to take his friend with him to visit the capital and to study medicine.” The meaning is may be interpreted various ways:

“He said that he wished to take his friend with him,

A “…and also to visit the capital and study medicine.” or

B “…that his friend might visit the capital and might also study medicine,” or

C “…on a visit to the capital, and that he also wished to study medicine.”

From the three different versions it will be perceived that this ambiguity must be met by using “that” for “to,” which allows us to repeat an auxiliary verb and by inserting conjunctions.

“In order to,” and “for the purpose of,” can be used to distinguish (wherever there is any ambiguity) between an infinitive that expresses a purpose, and an infinitive that does not.  “He asked his mother to call his friend, to (in order to) give him information about the homework assignment, and not to leave him unprepared.”

6. Repeat the Subject, where its omission would cause obscurity or ambiguity.

The omission is particularly likely to cause obscurity after a Relative standing as Subject: “He professes to be helping the company, which in reality is suffering from his attention, and (he? or it?) will not permit anyone else to give advice.”

The Relative should be repeated when it is the Subject of several Verbs. “All the pleasing illusions which made power gentle and obedience liberal, which harmonized the different shades of life, and which, by a bland assimilation, incorporated into politics the sentiments that beautify and soften private society, are to be dissolved by this new conquering empire of light and reason.”

7. Repeat a Preposition after an intervening Conjunction, especially if a Verb and an Object also intervene.

“He forgets the gratitude that he owes to those that helped all his companions when he was poor and uninfluential and (to) John Smith in particular.” Here, omit to, and the meaning may be “that helped all his companions, and John Smith in particular.” The intervention of the verb and object, “helped” and “companions,” causes this ambiguity.

8. Repeat Verbs after the Conjunctions “than” and “as”.

“I think he likes me better than you.”  Either “than you like me,” or “he likes you.”

9. Repeat the Subject, or some other emphatic word, or a summary of what has been said, if the sentence is so long that it is difficult to keep the thread of meaning unbroken.

“The country is in such a condition, that if we delay longer some fair measure of reform, sufficient at least to satisfy the more moderate, and much more, if we refuse all reform whatsoever–I say, if we adopt so unwise a policy, the country is in such a condition that we may precipitate a revolution.”

Where the relative is either implied (in a participle) or repeated, the antecedent must often be repeated also. In the following sentence we have the Subject repeated not only in the final summary, but also as the antecedent: “But if there were, in any part of the world, a national church regarded as heretical by four-fifths of the nation committed to its care; a church established and maintained by the sword; a church producing twice as many riots as conversions; a church which, though possessing great wealth and power, and though long backed by persecuting laws, had, in the course of many generations, been found unable to propagate its doctrines, and barely able to maintain its ground; a church so odious that fraud and violence, when used against its clear rights of property, were generally regarded as fair play; a church whose ministers were preaching to desolate walls, and with difficulty obtaining their lawful subsistence by the help of bayonets,–such a church, on our principles, could not, we must own, be defended.”

10. Let each sentence have one, and only one, principal subject of thought. Avoid heterogeneous sentences.

Source: ABBOTT, EDWIN A., M.A., HOW TO WRITE CLEARLY - RULES AND EXERCISES ON ENGLISH COMPOSITION.