This document discusses types of errors made by English language learners and strategies for providing feedback on errors in student writing. It divides mistakes into slips, errors, and attempts. Common error types include issues with nouns, verbs, subject-verb agreement, word choice, and sentence structure. The document emphasizes that mistakes are a normal part of language learning and provides tips for deciding which errors to address, such as errors that impede comprehension or common patterns. It also discusses using direct and indirect feedback, and strategies to help students develop vocabulary, grammar, style, independence, and self-editing skills.