1. from Badaling, please take the bus 919 and get off at Changping Xiguan (昌平西关)and then please transfer to bus 314 or 22 which could drive you to Ming Tomb directly.
Ps: bus 22 belongs to Changping District, so you couldn't search them out via the bus search tool supplied on this website.
2. every tomb in China here does has its own sacred way, so no transportation is needed. Well, these Mong Tombs are all located in a way.
3. From Ming Tomb, please take the bus 22 and get off at Lishuiqiao (立水桥). Here, please transfer to metro Line 5 to Huixinxijienankou and then metro Line 10 to Beitucheng. From Beitucheng, please take Line 8 to the National Stadium.
Ps: please refer to the Beijing metro map supplied on this website.