Getting a high-band score requires a lot of hard work and determination from every candidate. However, there is one thing that I highly recommend to every student, which is to practice, a lot of practice. People can learn grammar and vocabulary, and they can watch English movies or listen to podcasts, which are really useful. Nevertheless, one thing that really helps is to speak. You need to find some IELTS questions and start answering them today. First and second times it will be awful, and you will face many dificulties, but as you continue speaking, it starts to get better. I suggest practising until you are satisfied from your answer.