From Delhi :

1. Travel by air to Bagdogra from Delhi.
2. Travel by train (Rajdhani Express) to either :
3. Calcutta (Howrah) overnight and take the Darjeeling Mail from Calcutta's Sealdah station or
4. New Jalpaiguri on the Guwahati-bound train and overnight at Siliguri before boarding the 'Toy Train'.

From Calcutta :
Your journey starts at from 8 at Calcutta's Sealdah Station by Train 3143 'the Darjeeling Mail'. This leaves around 7pm for an overnight journey to New Jalpaiguriarriving just after 8am.

From New Jalpaiguri :
The 'Toy Train', connecting with the 'Darjeeling Mail', leaves at 9am, getting to Kurseong just before 2pm in the afternoon. Ghoom is reached a little after 4:30pm, with arrival at Darjeeling at around 6pm - just in time for evening dinner! An earlier train leaves at 7:30am; take a taxi to join this train en-route.
The return trip normally leaves at 8:25am - enquire before leaving for exact times.