So, a writer should make sure the pronoun is clear.
David and Bill went to the store, and he enjoyed his newly purchased candy bar and cherry pie. It was the best thing he ever tasted.
He = Bill
It = Cherry Pie
If that is the meaning the author intends, the sentence works. However, if he is meant to be David and/or it refers to the candy bar, then some reworking is needed. The his and he subsequently used refer to Bill as well.
Okay, so just remember... the pronoun refers to the closest, preceding noun.
Sometimes, the pronoun is used correctly, but the sentence is still suspect.
Several Miami strippers donated boxes of clothing, and they can be viewed at the church bazaar next Saturday.
Whoa. Wait a minute. Yes, they = boxes of clothing, but a reader might do a double take and think the strippers can be viewed at a church. That's a whole different story. *snickers*
Better to rework the sentence for clarity...
Several Miami strippers donated boxes of clothing, and these items can be viewed at the church bazaar next Saturday.
Also, if it's been a while since the noun the pronoun refers to was used, clarify by repeating the noun. You don't want to make a reader search back a couple of paragraphs to figure out who he/she/it is.
Furthermore, pronouns should not refer to something that hasn't been mentioned yet.
If it's cheaper, then definitely buy the red blouse.
If the red blouse is cheaper, then definitely buy it.
I could go on forever about pronouns, but the examples above cover a lot of material.
An exception (because there's always one, right?)...
Dialog is independent of prose. A noun mentioned in dialog, would not be the closest, preceding noun for the sake of a pronoun in prose.
For example, if a main character (Kevin) is highlighted in prose but mentions a Gary in dialog, Kevin is still the he when prose begins again.
For more information, visit this great post by Grammar Girl: Pronouns and Antecedents.
Is there an editing/grammar issue that's always caused you trouble? If so, share it in the comments so I can feature it in a future post.