Hi,
My $0.02 worth...
The time spent per day varies from person to person. The important thing is to be regular. Even if it's only an hour a day, that's better than doing nothing during the week and slogging during the weekends. And as for working vis-a-vis staying at home, I don't think that makes much of a difference either. Whether you work, are in college or at home, 1-2 hours of effort a day consistently through a four to five month period is what is needed. Another important thing is to not jump into a tough routine. If you are an engineer, then like me you've probably spent four years of total fun

, and suddenly jumping into a 3 hour daily study schedule will probably be something akin to culture shock

. So, build up to it. Start off with an hour or so, and build up to two or three as the CAT approaches.
And as for extra material, I would suggest reading a good newspaper everyday, to help build your verbal and RC skills. Especially the editorials, as they're quite long and usually of the same "interest" level as the RCs in the CAT.
Regards,
Mansur