Short, quick post: I’d purchased a Nexus S recently, and once I got back to India, I had to re-activate my connection again.
Unlike the iPhone, however, my Android was unable to pick up the settings automatically & I had to enter them manually. To do this, head over to Settings -> Wireless & Networks -> Mobile Networks -> Access Point names. Tap on the options button -> New APN & enter the settings as per your plan, as mentioned in my previous post comparing various Airtel GPRS plans.
Name: Enter a name to identify
APN/Address/Access point: airtelgprs.com for Airtel Mobile Office.
That’s it. Restart your phone(if required) and you should be able to start browsing.