I know there are plenty of posts about how to get to the Terracotta Army from Xian, but we lost 3.5 hours following them... not because they were wrong, but because things in China change more often than you would imagine.
So here's a guide on how to get to the Terracotta Army from Xian (anyway in the city) in a way that won't be affected by sudden changes.
Do not look for buses
As we read that there were some buses leaving from the central station we decided that it would be a good opportunity the see the city while going to the Army, even if we knew that the journey would be pretty long.
We soon learned there there are no more direct buses; we made the mistake to take one bus to get to the "tourist bus number 5" outside town and wasted more than 3 hours, not only because of the traffic, but also because Number 5 runs every 40 minutes!
Just take the underground
The best way to get to the Terracotta Army from Xian is taking the underground from any area in the city, just make sure to get to LINE 9 and stop at 华清池 (Huaqing Hot Springs).
From there you could take some buses (602, 303) and waste more of your time, or simply take a metered taxi (I prefer to use DIDI or any other APP), it will cost you 1 euro...
This is the easiest and fasted way!
And don't forget to read my posts on how to book a hotel or a train ticket in China, enjoy your trip!