For an easier but still less touristy sections, we suggest the Mutianyu section of the Wall http://staging.catherinelutours.com/itinerary/great-wall-at-the-mutianyu-section/ which is less than a 2-hour ride from the city center. You can either take the cable car up and down the wall or chairlift up and take a toboggan down the wall!
If you want to do the more adventurous sections and you are good physical condition, then you can choose one of the following routes:
Hiking from Jiankou to Mutianyu section:
http://staging.catherinelutours.com/itinerary/hiking-from-jiankou-to-mutianyu-great-wall/
Hiking from Jingshanling West to Jingshanling East
http://staging.catherinelutours.com/itinerary/hiking-from-jingshanling-to-simatai-great-wall/
Hiking from Huanghuacheng to Xishuiyu Wall section:
http://staging.catherinelutours.com/itinerary/huanghuacheng-xishuiyu-hiking-1-day-tour-8km5miles/
There are more details available on these pages so you may choose the sections that you are most interested in. We can also customize the tours to your preference.