A pronoun is a figure of speech used as a substitute for a noun, to avoid repetition of the noun.

Pronouns create two problems.

Confusion Over The Intended Antecedent

This problem mostly exists with beginning writers.

An antecedent is the noun to which a pronoun refers. The noun, in other words, for which the pronoun substitutes.

For example, if we write,

   I flipped through the book, put it back up on the shelf.

The reader understands 'it' refers to 'book'. 'Book', in this example, is the antecedent for 'it'. De-pronouned, the sentence would read,

   I flipped through the book, put the book back up on the shelf.

In a simple sentence, it isn't difficult for the reader to discern what 'it' refers back to, since there is only one noun, 'book', occurring prior to the pronoun.

When two or more nouns precede the pronoun, if the sentence has not been structured properly, there can be confusion as to which noun the pronoun refers.

For example,

   He dived into the ocean with a spear gun, shivering at its coldness.

When the reader encounters a pronoun, he or she looks leftwards to the nearest noun, assuming that to be the antecedent of the pronoun. In the example above, the reader would initially assume the coldness of 'it' refers to the spear gun, which makes no sense. The reader then has to feel farther back in the sentence, to arrive at 'ocean'. The reader, in other words, has to stop reading. Has to puzzle out the sense of the sentence. As a writer, you've just lost the forward momentum of your story. (There are times when you might want a reader to reread a sentence, for example to re-experience the unexpected direction in which you've taken him or her from the capitalized first letter to the closing period, but these rereadings should always be based on your conscious technical skill, and not on your clumsy grammatical errors).

So how should the sentence be written?

If we keep the pronoun, we have to rearrange the sentence so the actual antecedent to the pronoun, 'ocean', occurs just prior to the pronoun's placement.

   Holding a spear gun, he dived into the ocean, shivering at its coldness.

If we want the order of the words to remain as they were originally written, we have to eliminate the pronoun.

   He dived into the ocean with a spear gun, shivering at the ocean's coldness.

Either solution allows the reader to immediately grasp the images and sensations you've put into the sentence.

Note also that when the pronoun 'it' is used in possessive form, the correct spelling is always 'its', without an apostrophe, and never 'it's'. 'It's' is only used as a contraction for 'it is'.

The Abstractive Nature of Pronouns

This problem can exist with experienced writers.

A pronoun, by its very nature, is abstract. This abstractness can weaken your writing.

'It' does not conjure up an image as vividly as 'ocean' or 'book' does.

One of the commonly accepted rules of good writing is that repetition is to be avoided. Pronouns are a way to avoid repetition, but the abstraction they introduce as a solution is often far worse than the repetition.

Let's study a couple of variations of the same sentence.

   Breathing heavily, tiring, Brandon swung a tent pole at the bear, then threw his canteen at it.

Swinging a tent pole at a bear is a clear image. So is throwing a canteen. But notice how weakly the sentence ends, with 'it'. If you accept my idea, discussed elsewhere in this series, that the most important part of a sentence is the ending, this sentence fails. 'It' is not an image. It is only a reference to an image, and this once-removed evocation of an image will never be as vivid as the image itself.

So what can we do?

One solution is to simply repeat the noun, 'bear'.

   Breathing heavily, tiring, Brandon swung a tent pole at the bear, then threw his canteen at the bear.

Some of you might dislike the repetition, but your sentence is stronger in its imagery, ending with a word more quickly imagined.

Another solution, a better one, is to use a related noun.

When referring to the same 'thing' twice in the same sentence, the reader's imagining of that thing is often intensified if you move from the general to the particular.

   Breathing heavily, tiring, Brandon swung a tent pole at the bear, then threw his canteen at the yellow fangs.

In this variation, we've first established the image of the bear (the 'general'), then focused on the yellow fangs (the 'particular').

Note we don't say, 'its yellow fangs', because this would again introduce an abstraction into our sentence, albeit a brief one, but one which would still momentarily slow down your reader while he or she deciphered that 'its' meant 'the bear's'. "The', also, by its specificity, is an excellent way of conveying the 'thereness' of the fangs.

What about the use of a pronoun in 'his canteen'?

My belief is that pronouns referring to neuter nouns introduce far more abstraction in a sentence than pronouns referring to male or female nouns.

I am not suggesting that 'it' and 'its' should never be used in writing. But if you find an 'it' or 'its' in one of your sentences, consider using the 'general, then particular' rule instead, or a 'particular, then general' variant if appropriate.