For PRS ticket - Go to PRS counter with an application giving details of ticket and an original id card. Some charge will be taken and duplicate ticket will be issued.
For e-ticket - Get the SMS on your cellphone by logging in onto IRCTC. And by chance if you cannot show SMS/PDF copy on any electronic gadget then the TTE is liable to fine Rs. 50 after confirming the passenger details and verifying with id card. ( Incase of eticket show to TTE that you are searching the msg/email on your phone and do it for bit longer. The TTE will get irritated and will just demand an id-card and mark against your name. Probability of working of this...
more... tip is very low, say about 25%)