The official Indian Railways site at indianrail.gov.in isn’t quite user-friendly and it takes a couple of steps to check the availability of seats on any train.
If you are looking an alternative to the Indian Railways website, check the Cleartrip Calendar that combines train search and seat availability in one step. You just need to specify the source and destination railways stations, the class of the coach and your expected travel date.
The results table will display the list of trains available on the route as well as the booking status of individual trains. Red means that all the seats are booked, yellow mean R.A.C. while green indicates that you can get a confirmed seat on that date.
In case you find seats available on the train of your choice, Cleartrip even allows you to book the ticket right from the site itself. You can also check seat availability in Indian Railways using the MakeMyTrip, another travel and online ticket booking website.