talk to native speakers only and try to engage in conversations with them on a consistent basis if possible
when you write and speak, always keep the 4 criteria in mind such as vocabulary and grammar range. sometimes, try to squeeze in some advanced sentence structures and vocabulary appropriately
play it safe. Do not use any vocabulary you are unsure of, especially in writing
learn punctuation and spellings of most commonly misspelled words.
attend lots of trial exams at your local IELTS center and make sure your essays are examined by a certified native examiner
try timing your self and always leave at least two minutes for proofreading
remember listening and reading are the easiest sections to boost your overall score