JC, as Thinkfree said, which plan is best for you depends on your budget and what you want to do with your connection. I guess you've looked at the various BSNL plans, but I understand that it is sometimes difficult to estimate one's own needs.
Many young men who like downloading huge amounts of data often choose Home unlimited. The disadvantage is that, at 256 KB/s, it is much slower than the Limited plans, and more expensive than entry-level limited plans.
Personally, I've gone for the Home 500 plan with a 2.5 GB/month transfer limit (average of 80 MB per day), a speed of 2 Mbps and unlimited free time from 2 - 8:00 AM. I schedule larger downloads during the free time and I manage quite well within the 2.5 GB limit. However, my usage habits may not be suitable for everyone.
The Home 250 plan works out to an average of about 30 MB per day, and may be enough for those who use it only for email and browsing with occasional small downloads. But it does not come with night unlimited. Speed is upto 2 Mbps.
Even the Home 125 plan may be enough for those with very light usage habits. 150 MB/month, 5 MB/per day average. Upto 2 Mbps.
With Home 1000 and above, you can start doing some serious usage while reserving the really heavy downloads during free time.
Then there's Home Unlimited 1350, the advantage over UL 750 being the higher speed of 512 KB/s. The disadvantage again is the slower speed compared to Limited plans.
Of course, all of this information and more can be seen at the BSNL website. I've picked out some of them and presented them this way in case it helps you make a decision.