IELTS candidates should pay special attention to their spelling. Your IELTS writing will be much improved if words are spelt correctly. Keep a list of words that you spell incorrectly and test yourself on their spelling regularly.
When you have finished a piece of writing, edit it carefully and check for any spelling errors.
Read this post about editing your written work.
Here is a short recorded spelling test. There are five commonly misspelled words. Press play and try to write down the words immediately. You can press “pause” between the words if you need to. Listen to the recording as many times as you want to.
When you have finished, you can check your answers here.