MBA Preparation...honest advice needed.?

I'm doing my b.tech in electrical engg and have just completed my first year. I want to start my preparation for CAT, XAT, etc. from now on. I'm really fond of reading. However, my vocab isn't strong enough. I have my sister's T.I.M.E. study material. To improve my vocab. I have started reading word power, various novels, newspaper articles. I'm just a starter so I would seek some help from you guys... How should I divide my time and how much do I need to study to get into IIMs/Xavier's.