Originally Posted by Scifience

Taxi is fine; HMPS' unfortunate experience is not typical. You definitely will need to have the address written in Chinese characters, however, as the chances of getting a driver who can read English is near zero.

What hotel will you be staying at? I'd be happy to type the address out in Chinese for you. Still, if it's not a well-known hotel, you may find that the driver will call for directions (have the hotel phone # handy).

I'd recommend avoiding a tour company for the Great Wall trip. Many of the tours advertised include annoying shopping stops and the like and won't give you the flexibility to explore at your preferred pace. Public transit to the Great Wall is available (see Wikivoyage for details), but hiring a private car/driver for the day either via your hotel or independently is easiest.