Record the errors that you make during your perparation for the exam. Visit this list from time to time during the preparation period so that you can refine your error list and understand whether you are still making the same errors or not.
Knowledge of synonyms is very important as in the reading section it is not necessary that the text that appears in the question or passage also appear in the answers. In answers there might be alternate text, to the questions, having the same meaning.
Try to figure out your weak areas and work on refining them. For example, if you have good spelling and grammar but your vocabulary isweak, concentrate on increasing your vocabulary so that you have a chance to score high on the exam.
Understand the nature of questions completely such as for task 1 academic writing, there are variety of different options such as graphs, charts and maps. For task 2, there are different types of essays comprising of agree/disagree, etc.
During the exam, try to speak about topics, that you know well and also have a reasonable amount of vocabulary for. This is of course may not be possible to do for all questions, however as much as possible try to focus the area to easier ones. Thus, before the exam, try to think of vocabulary for some possible "specialist" areas, such as about football or your favorite restaurant, etc..
For the IELTS, be very careful to have clear handwriting. Some students may think that it is not important,however remember that the examiner should be able to read it clearly. Thus, each letter should clearly have only one option ,so that if any school student were to look at it, then they could clearly say what it is .
Be sure to have enough words for the IELTS writing task 1 and 2. For the task 1,it is a minimum of 150 words and for the task 2, a minimum of 250 words.In the exam,it may take a bit time to keep counting the number of words, so in your practice see if you are always writing a similar amounts of words for each line, such as 10 and then multiply it to find the amount you need:do not risk writing under the minimum amounts if at all possible.
Usage of useful expressions during speaking exam can really boost the speaking score as examiner is on a hunt for such expressions. Therefore, make a list of some useful expressions and use them in your daily life conversations. The more you use and practice them, the better it will be for your score in the exam.