Which datacenter to use

It depends on whether the traffic is routed east (India - SE Asia - Japan/Australia - Pacific - Fremont) or west (India - SW Asia - Europe - Atlantic - Newark). Well, since India is a big country, it could even depend on where you are in India. You can ping/traceroute both locations to see how the traffic gets routed. Or if you're not there, you can use services such as http://www.just-ping.com/ I believe they have a checkpoint in India.

See this forum post for files to download from all 4 datacenters. That should give you and idea where you should place your Linode.

http://www.linode.com/forums/viewtopic.php?t=2636