By this time, I hope that you must have gone through the last year Question Paper and the Sample Papers released by CBSE.
I am providing here the links for the same for your ready reference.
CLASS X (MATHEMATICS)
Sample Papers (1,2 and 3) with Solutions
HOTS by KVS MYSORE REGION
HOTS BY KVS DELHI REGION
HOTS BY KVS CHENNAI REGION
Question Bank by DOE
CLASS XII (MATHEMATICS)
Sample Papers (Released for 2009 Exams) here
Sample Papers (Released for 2010 Exams) Part 1 Part 2
HOTS by KVS banglore region
HOTS by KVS
Question Bank by DOE : For Commerce Students For Science Students
NOTE: For all other subjects visit official site of CBSE .