Imagine a choreographer with a troupe of dancers whose moves must be woven together into close and intricate dance, without blunder or collision: That is the author moving characters through scenes, directing the dynamic flow of action, and pronouns are essential to a successful 'dance.'

The right pronoun in the right place gives your language clarity and reveals scene and action. and keeps the 'dancers' from colliding. The wrong pronoun badly placed confounds the reader and obstructs the flow of the story, as well as the action.

The basic pronoun variations are easy enough: singular, plural; subject, object; gender; possesive. Even the most basic native speaker of English knows what they are. It is when to use which one where that can become problematic. Here are some things to bear in mind as you write and as you self-edit, that will make a difference when your work is in the hands of reader or editor.

Pronouns alone can't always get your meaning across.

They are useful to establish the characters in a scene into relation to each other, and to the actions, and also, by the way, establishes gender where it counts.

Pat and Leslie walked through the fields, their fingers entwined, a soft smile on her lips and he was happy inside though he didn't show it. Across the meadow, Billy, Sam, and Grayson were setting up lunch. They saw them and waved. They shouted in reply and came running over to them.

That sample tells the reader exactly nothing except that people are in a field, and at least one is male or female. Pronouns themselves don't always do the trick: Actual nouns come in handy sometimes.

Pat was happy inside, though his face didn't show it, walking with Leslie, his fingers entwined with hers. Across the meadow, his three sisters were setting up lunch. The girls saw them, and waved, and they shouted in reply, and came running over to them.

The pronoun must be placed to refer clearly back to the correct noun.

The unknown woman lay on the ground, witnesses and gawkers standing around the small group of medics. A girl ran up, and spoke to the medics. Their leader nodded and said a few words to his team who then bundled her up and carried her away.

So, who got bundled away? It could be the unknown woman, or the girl. The point is, imprecise pronoun usage creates confusion, and it is easy to fix: again, use a simple noun:

...who then bundled up the victim and carried her away.

Subject pronouns should not be used as object pronouns, ever.

If you would use "I" alone, then it is "(X) and I."

If you would say "me" alone, then use "(X) and me."

Lately, a lot of people who should know better--journalists and news anchors, for instance--use the subject form where the object form is called for. Getting it right is so easy, there is no excuse for getting it wrong, and the usual reason is ignorance. Ignorance of such a fundamental point of grammar can seriously damage a writer's credibility.

Getting the small stuff correct--or not--can determine whether your work ever reaches an editor.