I would suggest not to drop the sections or even every three sections.
I would have the top of the fence follow the fall of the land.
Here is what I do:
Let's assume the fence is 6 foot high. Then on one side I would drive a 2 x 2 into the ground. Then measure up 6 feet on the pole and mark that. Then screw a drywall screw into that spot and attach a line.
Then go to the down side of that side and do the same there. Now hook up the line on that mark and then that is your line to follow when hanging individual pickets. This way you don't have those un professional step downs and you have a straight line on the top.
Step downs, Ryan, are what un professional fence people do when they cannot figure out how to follow the fall of the land.
Even if you use prefabs fencing, you can do the same thing here. That is why on prefabs, they use only one nail per slatt. this way the section will "rack" and go down a hill.