Exam grades for IELTS are based on four section of the exam pattern i.e. Reading, listening, speaking and writing. There are four criteria for assigning a grade in speaking and writing sections. For maximizing the score proper understanding of the required criteria is essential for students. As an example, use of idioms to score high in vocabulary component. For grammar use compound or complex sentences.

How the writing test is graded
In accordance of the four key criteria, writing test is graded and marked from1-9.

Task Fulfillment: Develop all parts of questions and answers.
Coherence & Cohesion: Easy to understand writing skills referred to as the coherence. The quality of the sentence, paragraphing, structure, use of connective devices can best fit together with Cohesion.
Vocabulary: Use of higher level of words can score high in the vocabulary sections.
Grammar: Use a variety of sentence types, avoid grammatical errors and develop better writing skills.

How the reading test is graded
Reading test is too graded in accordance with four key criteria and marked from 1-9:

Fluency and coherence: Speak at the normal speed without excessive restarting and hesitation.
Vocabulary: Use of higher level of words, control word endings and pay attention to collocation. Students too should have ability to paraphrase and use colloquial language.
Grammar: Avoid grammatical errors while using a variety of sentence types. Don’t use a sentence that makes speaking difficult to understand.
Accent: the level of accent, intonation, rhythm and stress all influences the grade.