I asked around about what a taxi would cost and was quoted 350-400¥ return trip so decided to take the bus instead. We took bus 5(306) from the east lot of the railway station. It took an hour and cost 7¥ per person. The proper bus is a grayish green bus with green writing. The driver and ticket lady wear uniforms. There will be many touts trying to get you to take their bus, but resist. Apparently these non-official busses make many more stops along the way and charge a little more. The last stop is the Terra Cotta Warriors parking lot. We purchased tickets for 150¥ per person and an English speaking guide for 150¥. You can also rent audio guides for 40¥. If you have a good guide book you could probably do without a guide, but I was happy with the choice to hire one. There are many official government guides in uniforms and wearing their accreditations around their neck. Find one that you feel comfortable with.
You have the option of walking up the main street for about 15-20 minutes to the entrance or catch a shuttle cart for 5¥ One way and be there in 2-3 minutes.
I chose to see pit 1 first but that's a personal decision. It certainly is far grander than pit 2 or 3. It’s truly amazing to see and learn about the ancient history and the modern day discovery and restoration process.
You can easily spend 2 - 3 hours viewing everything. The same bus leaves from where it dropped you off and will take you back to the terminus at the railway station.
Wherever your plans take you in China, you've got to do the Terra-cotta Warriors.