Contorary to what Lonely Planet (May 2007) states, buses to Chengde depart from the Liuliqiao bus station in the south-west of the city centre and NOT from the Sihui bus station in the east of the city. I learnt this the hard way by going to Sihui first and then being told to go to Liuliqiao which happens to be on the other side of the city. The bus I caught took 4hrs when I was hoping it would take 2.5hrs as it didn't go via the expressway. It cost RMB73.
The hawkers around the train station were very aggressive trying to get us into their hotels, their illegal taxis, etc. The driver for the official taxi we took told us that the illegal taxis take you to the hotels and attempt to earn commissions from those hotels. For the official taxis, flag fall starts at rmb5, and almost every trip we took cost about rmb10. The taxis use there horns almost constantly here; most do not have working A/C, but it is pretty cool so no worries. The taxi we took from the train station claimed that it cost them 3 yuan to come into the main parking area, therefore he started the meter that much higher than usual (maybe it's true, we don't know.) It took about 15 minutes for us to reach our downtown Chengde hotel from the train station.
The train ride is about 4 hours long. The long distance bus which departs frequently from Dongzhimen station also takes around 4 hours. Both cost around 50 RMB.
If you have not been to the Great Wall at Simatai/Jinshanling then I suggest you take the one way train to Chengde and then you can stop at the Great Wall by bus on the way back to Beijing.