China has some fabulous luxury long-distance buses with air-conditioning and movies. Many intercity services depart more regularly than trains. However, buying tickets for them can be complicated if you don't speak Chinese -- you may end up on one of the cramped old-style affairs, much like an old-fashioned school bus. Drivers don't usually speak English, either. Taking a train or an internal flight is often much easier.
Most of Shanghai's long-distance services leave from the Shanghai Long Distance bus station, across the square from the Shanghai Railway Station in Zhabei. You buy tickets in the massive circular ticket lobby; allow time for the walk to the departure gate.
Shanghai Long Distance Bus Station (North Square, Shanghai Railway Station, 1662 Zhongxing Lu, Zhabei. 021/6605-0000).
