Don't be irrelevant. Although you can use your imagination to expand on your answer, if any part of your report is totally unrelated to the question and put in to just put up the word count, then the examiner will not take it into account and deduct it from the word count.
If you want to improve, there's no secret. Practice. Practice. Practice. You won't get better sitting and doing nothing. Even good English users need practice for the IELTS exam. It could make all the difference between your getting the band that you need, and getting half a band less than you need and having to wait 3 months to do the exam again.
