First task before leaving for station should be to check cancelled trains because many times train are not operational as per railway regulatory and order. Also due to some critical situation, some of trains might be temporary cancelled for some time. At the same time there is a possibility of withdrawing or terminating some train facility against some routes.
So to be on safer side and to ensure whether the train is running now or not, it is better to check that by either visiting to railway station enquiry department or just accessing this website.
You will face problem if the train is cancelled after you book the ticket for that train. At the time, you can visit to railway counter to cancel the ticket or you can cancel online from where you booked your ticket.
As an important point to note, you can get full refund of your money if you cancel your ticket within 72 hours from departure time in case the train is marked as 'CANCELLED'.
How to find cancelled trains list
Checking through IrctcPnr.org
This website will provide you the information about cancelled trains. Just input the cancellation date and click 'Submit' button. You will get the list of trains which are all cancelled on that particular date. At the bottom of list, will show the list update time.
Newspaper/Radio/TV
If many trains are suspended due to natural disaster, strike, accident etc they would most probably be published in newspaper, radio or TV channel for your information.
Go to Railway Station
If you visit the railway staion enquiry you would get information on what are trains are cancelled on that date.