train
I would ask the hotel for help booking train tickets because, unlike plane tickets, there aren't any discounts to speak of. Plus, trains sell out and it's well worth paying a small service charge to avoid an extra trip to the train station (Shanghai may well boast one of the nicest train stations in the country, but it's still not a pleasent place). The (fastest) z trains all leave at around 7p and arrive at 7a. TMK, the soft sleepers are all 2 per cabin; cost is comparable to flying.