I scored 100 marks in Chemistry exam in 2015 CBSE 12th board. Here is some advice from my side:

Chemistry is the easiest subject as compared to Physics & Mathematics. NCERT is more than sufficient to score good marks in Chemistry. Make your concepts clear and do practice all the NCERT intext questions. Make notes containing formulaes of each and every topic. Since Organic Chemistry is more time consuming, so in Organic Chemistry reactions, conversions, distinguishing tests and questions on identifying compounds A, B, C, D, E based on some chain of tests are important. Lastly, revise each and everything everyday. GOOD LUCK.