How do you study 4 ur exams?

My exams r in 16 days fm now n i had been studying 4 the last few days but i cant seem to concentrate n most of the things i have studied, i cant seem to rem them. I tried using diff colours to draw my mind maps 4 sci which most ppl say that it's useful bt not 4 me n doing many maths exam paper( almost 15 of them) which most ppl say that practice makes perfect...but i hv done so many papers but my grades r like deproving not improving..What should i do??