i've persuing b.tech3rd year.now after b.tech i want to do M.B.A..tell me how to prepare for the entrance exam of M.B.A.

although you are already late for preparation for competitive , it would be better for you to go for self study and prepare accordingly as per your schedule. there are enough books available in market. you can buy old preparation material also. or go for fresh material by brilliant etc

CAT or any Other MBA Entrance Exam includes Quantitative Aptitude , Reasoning , Critical Reasoning , English , Comprehensive English . Else TIME and IMS Are Best Institute for Coaching of CAT.