Study basic grammar. In order to speak any language correctly, it is necessary to study the grammar particular to that language. There are several distinct differences between English grammar and Korean grammar, for example:
Korean almost always uses the subject - object - verb order, and the verb always comes at the end of the sentence.
In Korean, it is pretty common to omit the subject of a sentence when the subject being referred to is known by both the readers and the speakers. The subject of the sentence may be inferred from the context or may have been referred to in an earlier sentence.
In Korean, adjectives function like verbs in that they can be altered and may take on different forms to indicate the tense of a sentence.
