I bought a Hutch sim card in the Gujarat area of India.
The store let me buy the sim card and it was activated within a few minutes. He did however tell me I had to come back with a photo of myself as well as my passport.
Check out Hutch's site for what information they require:
http://www.hutch.in/prepaid/download_prepaid_forms.asp
However despite submitting my documents to the retailer, I recieved a SMS message from Hutch a few days later warning that my outgoing calls would be suspended until they had recieved my information.
I decided to ignore the SMS and it was only when I was in Mumbai airport, I noticed that the outgoing service was barred but it didn't matter as I was leaving that day.
What I would suggest is buying the sim card from the network's (Airtel / Hutch) own store therefore they may be able to assist better with the ID requirements to ensure you have no problems.