In English an antecedent and its pronoun should be completely interchangeable. In other words, you should be able to replace the pronoun with its antecedent (or the antecedent with the pronoun) without changing the meaning of the sentence.
To follow the rule of interchangeability, you must make sure that the pronoun has an antecedent to replace. If the pronoun has no antecedent, the pronoun is stranded on a desert island, without a television crew and an immunity challenge.
Furthermore, the pronoun is a picky little part of speech. It refuses to replace any old word. If an antecedent is almost but not quite right, every self-respecting pronoun turns up its nose at the antecedent and calls the grammar police.
Sometimes the best way to avoid a pronoun error is to write a sentence that doesn’t need one. Keep that solution in mind if you begin writing a sentence and stumble over a pronoun issue.
Okay, time for the pronoun police to go to work:
Wrong: Lola’s a lawyer, and I want to study it.
What does it replace? Law, I suppose. But the word law is not in the sentence; lawyer is. Law and lawyer are close, but not close enough.
Right: Lola’s a lawyer, and I want to be one also.
Why it’s right: One refers to lawyer.
Also right: I’d like to study law, as Lola did.
Why it’s also right: There’s no pronoun in the sentence.
Also right: I want to make a lot of money, so I’m going to law school.
Another (trickier) example is:
Wrong: In Max’s poetry, he frequently uses cow imagery.
Who’s he? Max, most likely. But Max isn’t in the sentence. Max’s — the possessive noun — is in the sentence. You can replace Max’s by his (because his is a possessive pronoun), but not by he.
Right: Max frequently writes poetry with cow imagery.
Why it’s right: There’s no pronoun in the sentence.
Also right: Stay away from Max’s poetry readings unless you are really, really, really fond of cows.
Now you try. Which sentence is correct?
A. Lola has always been interested in archaeology because she thinks they spend a lot of time in the dirt.
B. Lola has always been interested in archaeology because she thinks archaeologists spend a lot of time in the dirt.
Answer: Sentence B is correct. In sentence A, no proper antecedent exists for they. Sentence B replaces they with the noun archaeologists.
If you’re still awake, go for it! Find the correct sentence.
A. In Lulu’s sonnets, she compares love to an unopened can of sardines.
B. In Lulu’s sonnets, the poet compares love to an unopened can of sardines.
Answer: Sentence B is correct. In sentence A, she has no antecedent. Because sentence B doesn’t use a pronoun, there's no pronoun error.