I think the most useful tools I used just before the exam may be "Academic Vocaburary in Use" (I took Academic Module), "Official Online Practice materials" and "IELTS 7 and 8". Of course, Sarah, my tutor, is awesome. She really took care of my practice, sticked to the same questions and focus on my weakness. Here is also a rumore that test centers in South West (in the US) may give generous scores than others. I am not sure that this is true but at least there may be room more to standarize the examiners' scoreing methods in writing and speaking sections. The most important tip to be success may be a good sleep and keeping your body in the best condition on the day of the test.
Keep practice and never give up.