Hi Sai Kiran,
Grammar is one of the areas where you can improve your accuracy significantly by working hard. Buy the reputed book on Grammar by Wren and Martin and understand the rules of grammar. Remember that Grammar at the end of the day is just a set of rules. Once you know all the rules, solving the questions will be very easy.
After going through the grammar rules, make a cheat-sheet with all rules numbered upwards starting from 1. The point of the cheatsheet is to use it while solving practice questions. Before checking the solution of any question, figure out what is the most appropriate rule to use in that particular case. If you feel that the rule specific to the question is not in your cheat-sheet, check the solution and add a new rule appropriately.
Once, you practice sufficient number of questions, your cheat-sheet will be exhaustive and you will notice a significant improvement in your accuracy.
Do check out our CAT Quotients on Grammar below.
Implementing the following strategy can help you increase your accuracy in Reading Comprehension:
a. Identify the theme of every paragraph while reading the RC for the first time.
b. Identify the specific questions. These are questions that pertain to a specific paragraph in the essay. These questions can be answered with greater accuracy.
c. For the 'generic questions', try to eliminate the least likely options. As a general strategy, choose the RC whose topic is familiar to you.
Try to answer at least three of the four questions in the RC. You can practise RC questions at the following links: