Going through the band score table of the IELTS Speaking test you will find the marking or assessment criteria organized in four categories.
Pronunciation is the most important factor as without correct and natural pronunciation-mind you not accent- communication could be impossible
Grammar variation also helps you deliver your speech correctly. You cannot always use the Present Simple tense, even if you are speaking about your childhood.
Lexical resource, in other words a rich and wide use of concise vocabulary, further enhances your speech delivery.
Fluency and coherence are made possible simply by combing all three previous skills into the desired level.
For more help, study the two Speaking-related articles on the site.