Fluency & coherence
You should be able to speak confidently and without hesitation when taking the speaking test, which primarily assesses the test-English taker's language fluency. If the test-taker can speak English fluently without stuttering, he or she will have a better chance of receiving an eight-band score on the speaking test.
The examiner may be impressed if you utilise idioms while speaking and also explain what they originally meant. The examiner expects you to use some complicated phrases when presenting the scenario, and you should be able to explain the meaning of the complex words that are used. The examiner will recognise that you are knowledgeable about the subject if you speak on it with ease without stopping to consider what to say next and may award you an 8 band score.
Grammatical range & accuracy
Here, the examiner will determine whether the speaking is organized. If your command of the English language is not so strong, you can still manage when writing, but it gets more difficult for non-native speakers to talk smoothly when speaking.
If the candidate speaks continuously and fluently without any efforts from the examiner and if the test taker is able to pronounce all the complex words during the test, he has high chances of getting a high band score.