I would suggest you to prepare for the exam along with your boards, Mostly students start their preparation from class 11th or 12th. Here are some of the important tips which are basic yet impactful, you can follow..

Know the CLAT paper pattern, marking scheme, changes in previous year, latest trends and participating colleges. 

It is not the quantity of books but the quality of books which matters. So make sure you have a selective yet good books with you. 
 Start with previous year CLAT question papers and previous year papers. 
 Be updated with General awareness, current affairs updates and even legal updates. 
 Work on your vocabulary. Read newspapers and relevant novels. This will also help you in increasing your speed. 
 Areas of Law to be understood in basic form includes: Law of Torts, Law of Contract, Constitutional Law, Criminal Law and some understanding of Family law. 
 Attempt online and offline mocks test. There are sectional and full length mocks available as well. Material you can refer to are: -Previous year question papers -Norman Lewis- Word Power Made easy -Verbal and Non Verbal Reasoning- By RS Agarwal -Universal guide to LLB Exam -Pearson GK Module -Monthly magazines on GK, Current Affair, Books and Novel Hope this helps.

Good Luck!!

Hello Aashna, 

It really depends when your 12th board ends. if they are ending in march, then you can join some coaching classes for a crash course and can take test series coachings. This might be easy for you considering the amount of time you will have.