How to buy apple iPhone 5 AT&T on contract basis?

I'm from Delhi, India. Any help would be greatly appreciated.

In order to get a phone on contract, it is required for AT&T to conduct a credit check. A credit check helps them make a decision on whether they'll offer you a phone on contract.

They will ask you for your personal details, including sources of identification as required in order to complete the application.

Once your application is successful, and your credit history is good, you might be asked for bank details that allow direct debit/bank draft transactions. If it is not mandatory, just your mailing address to where they can send your bills. If there are any upfront fees, they'll need to be paid in advance before they connect your phone.