When adverbs modify verbs (or verbals), they nearly always answer one of these questions:
Sometimes phrases or clauses are used as adverbs. They answer questions like those above, as well as these:
When adverbs modify adjectives or other adverbs, they usually qualify or intensify the meaning of the word they modify.
Be careful not to use adjectives in place of adverbs, even if you are accustomed to hearing such usage in casual or nonstandard speech.
Adverbs (smoothly, efficiently) must be used to modify the verb runs.
Only an adverb (really) can be used to modify an adjective (slim).
Exercises:
Adjectives and adverbs 1
Adjectives and adverbs 2
Adjectives and adverbs 3
Verbal phrases