Proper pronunciation allows for clear understanding between the speaker and the listener. If words are pronounced improperly, the listener may not entirely understand what the speaker is attempting to convey, especially if the word that was mispronounced sounds similar to another word with a different meaning. Since language is used to express a thought, proper pronunciation -- including a speaker's accent -- is essential to ensure comprehension.
Similar to the importance of pronunciation, accurate intonation patterns are an essential element of ESL speaking skills. Intonation means how clearly you speak by stressing specific syllables or words of a sentence. Although the rise and fall of speech is an important element of intonation, stress plays a more significant role. The meaning of a sentence can drastically change based on word stress. For example, in the sentence "This bag is mine," if you stress "this," the meaning of the sentence changes: "This bag is mine (not that bag)." Similarly, if a speaker stresses "bag" he is trying to convey that the bag is his, not the notebook or the pencil.
Natural pacing means how fluid your speech is. Native English speakers speak with a clear and fluid pace that helps the flow of the ideas they are trying to convey. Hesitations or pauses within a sentence can impede comprehension, as the listener must increase his focus in order to understand what the speaker is trying to express. Pacing is a difficult skill to master and requires many years of ESL studying before it is natural.
A strong understanding of grammar is the foundation of speaking in English. Without it, a speaker will struggle to formulate sentences and therefore will have trouble conveying his ideas. Similarly, effective speaking skills require a large vocabulary. Grammar is the ability to combine words together to create sentences that are clearly understandable. Although perfect grammar is not essential to communicating in English, it is a key element in speaking naturally. If an ESL student wishes to convey a complex idea, proper grammar is required to express it; simple grammar can allow you only to "get by." However, if a student is serious about the English language, a deep study of grammar is required, although grammar does not need to be studied as strictly as other aspects of the language. Exposure to the English language in itself is an effective form of studying grammar and the rules of the language.