if you are preparing for the IITJEE 2012,you should strengthen your strong areas,build up your speed and try not to do silly mistakes because your 1 mark down would drop your rank to about 200-300 below.
If you are preparing for IITJEE 2013,your should study each and every chapter thoroughly and strengthen your concepts and practice to apply the concepts in each question correctly as quick as you can and be persistent.
The following books would be useful for you:
For Chemistry:
Organic:Morisson & Boyd,Paula Yurkanis Bruice
Inorganic:NCERT,JD Lee,OP Tandon
Physical:OP Tandon,book authored by K.Rama Rao
For Maths:Arihant series books,ML Khanna
For Physics:HC Verma,Resnick Halliday
Hope this works.