One strategy for teaching adjectives to adults is to have the students pair predicative and attributive uses of the same noun and adjective. The attributive form places the adjective before a noun in a phrase. The predicative form places the adjective after a verb, the easiest being conjugated forms of to be, i.e., is or are, in a declarative sentence. For example, the attributive phrase "the red car" is paired with the predicative use of the adjective in the sentence, "The car is red." The attributive form may be difficult for non-native English speakers, because many languages place adjectives after the noun in the attributive form.
Non-neutral adjectives -- that is, those adjectives that can change meaning between the attributive and predicative forms -- can be clustered together in the same way irregular verbs are, for special attention. For example, when the phrase "a certain time" is used, it doesn't mean the same thing that is indicated by "he was certain he was right." Pairing adjectives that are the same word with contexts that render the meanings different requires specific attention to those dissimilar contexts through exercises that drill the student.
Some adjectives are closely related to adverbs, and many of those adverbs modify the adjective with the suffix "-ly." Paring these related adjectives and adverbs is useful for teaching the distinction between adjectives and adverbs. For example, "He is my former boss" can be paired with the sentence, "He was formerly my boss." Sentence combinations like these can even join opposites, like loud-and-loudly alongside quiet-and-quietly, or possible-and-possibly alongside impossible-and-impossibly.
Homework can employ the daily newspaper. Students read various assigned sections of the newspapers, like the top story, an obituary or a horoscope. The students are directed to identify and underline every adjective they find. After identifying the adjectives in the assignment, they have to use their dictionaries or their notes to change each of the adjectives in ways that change the article but still make grammatical sense. They read their changes in class, which may create some hilarity.