CAT

CAT is all about your Mindset + Luck + Preparation + Approach. Within a set limit of three months you can only work on all other parts other than "LUCK".
Set your plan right. Work on your plan and identify your weakness and strength. Get a materiel right. Try to plan and identify above stated things within a week. Set your plan agile and keep buffer time for revision and solving mock test papers.
Start with your verbal and quantitative practice in parallel. 3 months can make or change the game, time management is very important at every single point of time till the final day and even on the day.
Keep positive! Solve questions in a specified time frame this will help you in doing questions in time. Maintain a good balance between your accuracy and solving time.
Be focused and calm. For the last month keep all the formulas and tricks handy and revise on a daily basis.
Remember not to be emotional while solving or appearing for exam. Manage your time wisely.
Remember:
A goal without a plan is just a wish.

Hello Brundhan,
Your graduation score is fine.
Top colleges providing MBA/PGDM in India are:
IIM-Ahmedabad
FMS, Delhi
IIM-Bangalore
ISB-Hyderabad
IIM-Calcutta
IIM-Lucknow
XLRI-Jamshedpur
IIM-Indore
Narsee Monjee Institute of Management
Symbiosis Institute of Business Management
IIFT
JBIMS
SP JAIN
MDI-Gurgaon
Not all, but most of the institutes accept CAT.
And the cut-off percentile for each institute varies every year.
If you happen to score around 98 percentile, you will increase your chances of getting a call from IIM.
If not then you will surely get into any of these top institutes.
Try to target IIMs. Even If you fail to achieve your desired percentile, you will still not lose the chance of studying in one of the best institutes in India.
Also, if you want, you can appear for XAT, SNAP and NMAT.
XAT is for XLRI, SNAP is for Symbiosis group of colleges and NMAT is for Narsee Monjee.
Also, don't forget that academics too matter for the admission process.
Good luck.