Mock tests are usually designed a bit tougher than the actual exam to prepare the candidates for the examination. If you are getting 600 mark in the mock tests of NEET out of 720, then you can expect around 630 in the actual exam. And it is not difficult to get 650 marks in Mock tests as you are already getting 600 marks. Go through the results of last few mock tests of yours and analyze your weak areas from there. The places where you are making more mistakes or you are leaving that part - find out this and work on them. Read those chapters again from the start and then solve exercises. If this has numerical problems so first know the theory then solve the numerical. This is how you can increase your score in the mock tests. Along with this, keep giving exams on a regular basis and solve previous few years' exam papers. Biology is the most important part of the exam. Human physiology and Genetics and Evolution, and Diversity in living organisms carry maximum weightage. So focus more on these chapters. Give exams particularly on these. Many questions come from p-Block Elements, Coordination Compounds, Thermodynamics, Equilibrium as these chapters carry maximum weightage in Chemistry.