Coaching classes will help you to get idea about how to prepare.. and they give you some kind of structure in your preparation and materials. Apart from joining coaching class try to pend time on all 3 sections quant DI and verbal..
For Verbal-- improve reading skiills and reading speed.. (This helps u across all sectionss).. Improve vocabulary by reading a wide range of articles and newspapers.. mantain a notebook where u note down words.. improve grammar basics and keep practicing RC's and other question types regularly..
For Quabt, learn concepts from coaching classes and practice from materials and online tests.. For DI/Reasoning, keep solving as much as you can and as you keep doing it, you will get a hang of it and you will be able to se patterns..
TIME Aimcats do help in preparation and TIME online tests help you a lot..
How many hours depends on your current knowledge levels and where you want to be..This you have to take a call.. this you will figure out as you start preparing..
Hope it helps.. (Source: taken by R.Vishal answer http://mbabug.com/qa/1013/2012-prepartion-strategy-calendar-when-start-what-read-about)