You can book train tickets online at Indian Railways official booking website http://www.irctc.co.in/ You need to register on this website and then proceed to payment via Credit Card , Credit Card needs to be verified by Visa / Master Card . Choose the option of "e-ticket" , after ticket conformation you can print the ticket .
But keep in mind , trains in North India mostly travel late , so plan you schedule accordingly ! !
You may also book tickets from Local Travel Agents. They charge us ( Indians ) 2% extra for Card payments , they might make you'll (NRIs) shell out 5% more for Card Payment ! !
Wahegurji ka Khalsa ,Wahegurji ki Fateh