Upvote:3
If you are a foreign tourist, you can use the foreign tourist quota which reserves a small number of seats on each train. This quota is separate from the normal quotas and may be available even on a train which is nominally full.
The catch is you must be a foreign national on a tourist visa to use the quota, and you can only purchase the tickets at major railway stations in India - you can't purchase them online or via an agent. Check online to see if the nearest railway station has a foreign tourist quota office.
Upvote:5
When the train is full i.e even getting a tatkal ticket is not possible then there is only one option of boarding the train and that is the general compartment ticket. It might turn out to be the worst travelling experience for you as apparently there are no limits for the number of people travelling in general but that also depends on the train and the place you are travelling to. At times it will be fine for short journeys, but longer travelling time will just add to the misery. General ticket can be bought from the station where you are going to board the train.