In order to identify DIDLS terms, you will need to first pay attention to the "diction" of the author - the implication of his or her word choice. For example, you must ask yourself why the author chose to use certain words over others. What might the purpose of this be? Perhaps the author wrote the word "chuckle" instead of "laugh" in order to set a particular tone or to let the reader know about a particular character to help characterize that person. Ask yourself, for example, what makes a character "mature" instead of just "old."
The second step you'll need to take is to identify some imagery in the passage or chapter - vivid descriptions or figures of speech that help you, as the reader, identify the author's tone. To do this, you may want to look for and identify metaphors, similes, personification, hyperboly, understatement, synecdoche, oxymoron, paradox, overstatement, symbolism, irony, puns, and allusions. Also look for sound devices, like alliteration, repetition, assonance, consonance, onomatopoeia and rhyme. In Lord of the Flies, what might the pink conch shell and the trapped wild pig symbolize? Are they metaphorical?
Next, look for specific details that the author either chooses to include, or chooses to omit. Details are different from imagery in that they are facts that don't have a strong sensory appeal. For example, the name of a character in the story might help to establish the tone by reflecting intelligence or education or a lack thereof. Is it figurative? It may serve as a symbol for a concept or idea. In Chapter 1 of Lord of the Flies, the chubby boy introduces himself to Ralph as "Piggy." This is an important detail that could give you clues as to the author's tone.
Pay attention to the type of language that is being used by the author. Is it poetic? Formal? Does the author use a lot of slang words and colloquial vocabulary? What impression does that give you as the reader?
Last, pay special attention to the syntax used. This means sentence structure and how it affects your perception as the reader. For instance, does the author use parallel structure, similarly styled sentences, to convey interconnected emotions and ideas? Or does the author use shorter sentences to convey a passionate or flippant tone? Longer sentences might signify a more reflective, philsophical tone.
As the reader, you can look for certain clues which present a shift in tone. You can look for key words like "but," "nevertheless," or "however." You can also pay close attention to any changes which occur in punctuation, sentence length, paragraph divisions, or diction.