How can a writer improve their writing?

"How can a writer improve their writing?" Start by brushing up on your grammar skills. Remember the rule about pronouns agreeing with their antecedents? "A writer" is only one person. Therefore the pronoun "their" is incorrect, as it is a plural form. If you mean yourself when you say "a writer", your question should be phrased this way: "How can I improve my writing?" Or, "How can a writer improve her writing?"