Read the assigned passage carefully. Underline strong or unusual words that help the author communicate his message. For example, words like "amazing" or "perfect" may suggest a sales-pitch, or they may be used to sarcastically communicate a value judgement. Use the context to help you determine which meaning is intended.
Formulate a strong thesis statement. Your thesis should clearly state how the author uses language to reach a specific goal or communicate a message. For example, focus on the use of gender-specific pronouns to appeal to a certain type of person, or the strategic use of slang to set a tone or develop a character.
Include different aspects of language in each supporting paragraph. For example, focus on how language is used to set the tone through word choice in one paragraph; how it contributes to character development in another; and how the sentence structure works to communicate the author's ideas.
Use expected vocabulary to support your thesis. Write formally, using the third person. Readers expect to see words such as "sympathetic," "authoritative" or "persuasive" in your discussion of tone and the author's purpose. Tonal language also facilitates a discussion of character, with "melancholy" describing a different person than "exuberant."
Write a strong conclusion. Concisely restate your thesis and main supporting points. Follow this statement with a brief suggestion of ways to expand your ideas. For example, argue that the language used by Edgar Allen Poe set an ominous tone so effectively that some of his images, such as the raven, have become cultural symbols in America.