When preparing for IELTS, it is essential that you first determine your strengths and weaknesses. Take practice tests for reading and listening, and (if possible) hire a tutor to assess your speaking and writing skills. From there, you will know which areas require assistance, and you can focus on them directly.
In addition to this, I recommend the following to all students:
Understand the test - How many sections does it have? How long are those sections? How much time will you have per section? Knowing the format of the test will ease your anxiety and help you focus your learning as you practice, practice, practice.
Create realistic goals - After determining your weaknesses, set attainable goals in these areas. Learning a new language takes time and patience, and setting unreachable expectations for yourself will only discourage you. By setting goals and benchmarks that you can achieve within a reasonable time frame, you will be able to recognize your improvement and stay motivated.
Find interesting English material - What better way to acquaint yourself with another language than to surround yourself with it? Find podcasts, TED Talks, television shows and movies, blogs, and newspapers that are in English, and then dedicate a portion of your day, EVERY DAY, to reviewing these resources. Finding English resources on topics you enjoy will help you learn the language more quickly and effortlessly.
Talk to native speakers - If you want a Speaking band score of 8 or above, it is imperative that you talk with native speakers. This will greatly help your fluency and pronunciation. Find a buddy, line up Skype calls, or find a native speaking coach. Just keep in mind that simple conversation isn’t enough - you must practice IELTS-specific speaking strategies.
Make English a habit - Very simply, making something a habit (in this case English) will help you reach your personal goals more easily. Fit English into your life wherever possible. This means thinking in English, getting your news in English, writing your grocery lists in English, using new vocabulary in your day-to-day life, etc. This will ensure your English abilities come out in many different situations - even stressful ones like taking IELTS.