hai.

Study the concepts in depth, don't read superficially.
Try to clock 100 hours a week. That is the ideal time, but if you are multitasking then try making atleast 6 hours a day, i.e 50 hours a week, and even if it's little time try to grasp concepts and revise. 
Maintain your health
Sleep is crucial, else you'll get exhausted before time.
Form a study group, discuss with friends
Stay motivated.
No pain no gain, you won't get this opportunity again. Make the most of it.
Donot waste time, invest time.
Revisions are the most important
It is said that hand written notes are well remembered than printed material, make your own notes, keep reading it again and again.
The best books you can refer to are the NCERT, always remember ncert test is the key go through each and every thing in it
For biology, refer the following.
1) Trueman's Biology vol 1 and vol 2
2) Dinesh- Objective biology
3) Pradeep publication Biology
4) GRB'S Publication Biology.
For Physics refer to he following books.
1) H.C.Verma - Concepts of Physics.
2) D.C Pandey - Objective Physics.
3) Fundamentals of physics by Walker
4) Problems in Physics by I.E.Irodov
For chemistry you can refer the following books
1) O.P Tandon - Physical Chemistry
2) Morrison and Boyd - Organic Chemistry
3) Modern ABC's of chemistry
4) J.D.Lee Inorganic chemistry
5) Dinesh
Ncerts are mandatory to have, refer the rest of the books and find out which one suits you. I would advice you not to buy all the books but to refer them and see which one is better for you.
In the end it doesn't depend upon which book is better but how good can you understand the concepts
Also, for the general knowledge subscribe magazines, they will be useful.
Hope this helps.

thank you