Veeeerrrrryyy good question......

On the modern "D" trains there is a luggage compartment close to the entrance to each carriage but it fills up quickly. Make sure you get on promptly to secure a place

If they are full then there is often space behind the first seats in the carriage that you can use. What you can't do is put them in the overhead luggage racks - the train staff are super-vigilant re risk of luggage falling off these and won't allow any "overhang"

The older, slower trains are rather more a free for all re luggage but in all honesty I couldn't recommend travelling on them unless there isn't another option

Make sure you are organised re buying the train ticket. It is very risky to just turn up at the station to get a ticket, I usually get the concierge to get the exact train ticket I want a couple of days before I need it - they charge about RMB20 for this service, well worth it

nickyboy