Learn more about Grammar:
Adjectives: An Easy Guide with ExamplesAdverbial Clause: Definition, Meaning and ExamplesAdverbs: Definition, Meaning, Usage and ExamplesAnalogy: Definition & Meaning (with Examples)ArticlesBad Adverbs: What Makes an Adverb "Bad" and Why (with examples)Clauses: Definition, Meaning, and How to Use ThemConjunctions: Definition, Grammar Rules and ExamplesCoordinating Conjunctions: Definition, Meaning and ExamplesDangling ModifiersDeclarative Sentence: Definition, Meaning and ExamplesExaggerationHomophones: Definition and ExamplesInfinitivesInterjections: Definition, Meaning, and ExamplesIntransitive Verb: Definition, Meaning, and ExamplesNouns: Definition, Meaning and Types Explained (with examples)Participles PluralsPrepositional Phrase: What Is It & How to UsePrepositionsPronoun: Definition, Meaning and Types Explained (with examples)Split Infinitive: The Complete Guide (with Examples)Subordinate Clause: Definition, Types, and ExamplesSubordinating Conjunctions: What Are They? (with Examples in Sentences)The Complete Guide to Transitive VerbsTransition Words and Phrases in EnglishTypes of VerbsVerbs: Types of Verbs, Definition and ExamplesWhat Is Symbolism in Writing?Word ClassesWhy should I avoid adverbs in my writing?

Overuse of adverbs is the hallmark of lazy, cluttered writing. Good dialogue should use strong verbs rather than '-ly' adverbs. Often the adverbs mean the same as the verb and become redundant, leading to messy prose.
The most common (over)use of adverbs is to modify the verb said, e.g. "I'm leaving," he said angrily. By reducing these adverbs, the author allows the characters to convey the emotions of the dialogue themselves. Instead of telling the reader, they are able to show them. e.g. He thumped his hand on the desk. "I'm leaving."
As a general rule, writers should use no more than one adverb per 300 words. You can either replace the '-ly' adverb with a stronger adjective or verb, or remove it if it is obsolete. It is not necessary to remove every adverb, but limiting them will help strengthen your writing.