You can use
the Rail cum Road ticket facility to travel by rail
to Tirupati, and from there, by road to Tirumala. You
can present your rail cum road tickets at the Sri Venkateswara
Bus Stand in Tirupati, and in exchange, receive a bus
ticket to go to Tirumala.
Railway Reservation Offices
There are Railway Reservation
Offices at both Tirupati and Tirumala, from where nationwide
reservations can be made. Credit cards are accepted
at the Tirupati Railway Reservation Office.