While we were in India we traveled from New Delhi to Agra on the Shatabdi Express. It all turned out well and I recommend this train but we almost fell for a scam when boarding at the New Delhi Railway Station.
I had purchased the train tickets in advance through Cleartrip and printed out the electronic reservation. When entering the gate to the platform where luggage is screened we were asked to show the ticket. The person told us the ticket could not be used and had to be exchanged for a boarding pass. He pointed us to an office across the street where this could be done. We went to this office, where they told us we had failed to reconfirm the ticket 4 hours in advance and therefore our seat was given away. They then offered to help us find alternate transportation. This didn't seem right so we went back and tried to enter the platform again. We were stopped by a different individual who told us our ticket could not be used and pointed across the street to another office. This office had a similar story that we were wait-listed. We went back again and watched until no one was at the gate and made our way through and on to our train. Our seats were open and there was no problem when the conductor checked the ticket.
We now realize that none of these individuals at the gate were railway officials. They are simply trying to distract you long enough so that you miss the train and have to seek alternate transportation at great expense.
If you purchase tickets through Cleartrip, they are confirmed and no additional reconfirmation is required. The ticket that they provide can be used directly and does NOT need to be exchanged for a boarding pass. When anyone asks to see your ticket, ask to see their ID!
Agra was fantastic; you don't want to miss it.