CAT

You need to appear for one of the entrance exams like CAT, MAT, XAT and CMAT and based on your scores, you can apply for individual colleges. You can also take the UPTU entrance exams for management.
I, however, would advise you to look for some good colleges (Tier-1) like IMI New Delhi, MDI Gurgaon etc., but to get into these colleges you need to appear in CAT and score above 80 percentile. So, take a wise decision.

Hi,
You can either download it from the internet or can purchase it from a bookshop. There are many publishers, Arihant being an example.

Yes, other than CAT you can appear for MAT, XAT, CMAT, ATMA, SNAP, NMAT, etc. All have their respective official websites. Do check them from time to time, browse through MBA education portals. These exams also get published in English newspapers.

Yes, there is negative marking.

Yes, why not. but Institutes like JBIMS are the most sought after MBA institutes after IIMs so you need to be among the top percentile holders in CAT or XAT to get admission there.

CAT score is valid for 1 year.

You need to score more than 95 percentile in CAT exam. Since your graduation percentage is low, a high CAT score will help you.

Yeah, you will get some relaxation as you belong to the reserved category.

Following are the good colleges to pursue MBA:
1. IIMs
2. IITs
3. FMS-Delhi
4. JBIMS
5. SP JAIN
6. NITIE.