The Great Wall at Mutianyu is a little further from Beijing than the most popular section at Badaling, but it doesn't get as crowded.  This section of the Wall is fully restored, there are hand rails to help you up on the very steep parts and the views are spectacular.  

There are many day tours and even mass transit bus services available to this section of the Wall. Bus Line 867 goes straight to the Wall at 7:30am and 8:30am and leaves the Wall at 2:00pm and 4:00pm. Note, however, that some 867 buses do not go to the Wall, but only to the terminal in Mutianyu proper, so ask the conductor before you board. Also, note that the Beijing bus terminal for 867 is located a short walk from the main terminal at Dongzhimen station.

The other way to get there is to take the 916 Bus from Dongzhimen Station but it will stop at Huairou Bus Shelter. From this Shelter you can take minibus owned by locals for 40-50 Yuan to the gate of Mutianyu. Or you can take a rented car. There will be people approaching you to offer you their car or minibus. They are OK and friendly. But you still need to be careful and alert.

This part of the Wall is not as crowded as others and the Wall and steps are in good shape. There are two cable cars that will take you to the top of the Wall and back down again. There are two cable car companies.  If you walk on the top of the Wall to the opposite side you will have to buy another ticket. If you plan to walk this far, buy a one-way ticket only from the initial car company. You can buy tickets at the top of  the wall too but it will cost you  a bit more compared to the two-way ticket at the entrance. There is also a luge you can use to return to the bottom.

There is water available at the top of the Wall but it will cost you a little extra. Toilets are limited at the top of the cable car routes. Plan accordingly.

There is a Subway fast food restaurant at the base of the Wall for food to take to the top. There are also many souvenir vendors at the base you will need to make your way through to get to the Wall.   

Plan 3/4 of a day.