1

Tickets can be purchased online through the official china rail website or through the website of an unoffical ticket agent who must either purchase them from the official site, or from the station or another official channel on your behalf.

The official site has been discussed on these forums before. General consensus is that it is impractical for a tourist visiting China to purchase tickets there, due to credit card limitations and lack of english website.

Unofficial sites like http://www.travelchinaguide.com/china-trains/ offer a booking service, but with a relatively large fee.

2

If I show up on the station (Beijing West, I think), is it possible to buy tickets there for same-day departures?

3

To Xi'an? Probably not

4

I got a Chinese friend to order for me, but I have to pick the ticket up at Beijing West train station. Is that cumbersome, or straightforward?