From Xi'an to Mount Huashan:
Take the bullet train from Xi'an North Railway Station (西安北) to Huashan North Railway Station (华山北).
Time: 40 minutes
Cost: 50 CNY, second class
Departure: approximately every 30 minutes
At Huashan, there are special green minibuses outside the station that go to the mountain entrance for 10 CNY.
From Mount Huashan to Xi'an:
Option 1: Take a taxi from Dongshanmen Parking Lot to Huashan North Train Station. It should cost about 25 CNY. Take the bullet train back to Xi'an. Same price and leaves about every 30 minutes.
Option 2: Take the Tourist Bus Line 1 which leaves from the Dongshanmen Parking Lot at 1700 and goes to the Xi'an Train Station by the North Gate, costs 22 CNY and takes 3 hours.