The speaking part is usually a conversation about you, your plans for the future, your past studies, the reason for which you are taking the IELTS, your country, your town. Therefore be prepared for these subjects. You should prepare something to say about them. In addition, the examiner will show you a card with an argument you are supposed to discuss. The thing you have to remember is: use easy words and expressions if you are not very confident and everything will go well. To be able to comunicate what you think is far more important than doing it with a perfect English accent. Therefore, don't worry if your pronunciation is not exactly a British one. That's not the main point. Your understanding of what the examiner says and the ability to comunicate without grammatical mistakes is...