The GMAT or the Graduate Management Aptitude Test is required if you want to do apply to a business school.
The GRE is required for other Post Graduate Programs in your field/subject.
Good business schools require at least 650 score in GMAT so you should prepare seriously.If you aim fora dream university like Stanford or Harvard in US then prepare to aimfor a 720 and above score.The higher the score the more is the chance of your admission
At present in Hyderabad Best B-Schools as per my research are:-
ISB-Indian School of Business
NMiMS-Nursee Monjee Institute of Management Studies
Ethames Graduate School-UK, India Campus (250 acres Residential Campus to start in 2012 near Gachibouli/Day campus already started)
XLRI- Hyderabad (campus about to start)
IIT-Hyderabad (located in Medak District)
IBS-Indian Business School
IPE-Institute of Public Enterprise
Editor- Himachal Spider