Gary,
I have 6 fieldstone retaining walls in my backyard. The stones are roughly basketball size (some larger, some smaller) and weigh about 50#. I used a JD 450 garden tractor with FEL to bring the rocks to the area directly above the wall. That way the approprate rock could be rolled downhill and into its place on the wall. Of course, sometimes the selected rock didn't fit and another rock would have to be selected.
Start the wall with 1 course of large rocks below grade for a foundation. Since these are fieldstones, each rock must be hand-positioned just right to interlock with the adjoining rocks. Step the rocks back as the wall gets higher. Landscape fabric placed behind the rocks prevents dirt from washing through the cracks to the face of the wall.
Some of my walls are close to 6' high and I can drive my tractor within 1' of the top of the wall when cutting the grass. The main thing to know when building with fieldstone is that you put the mass of the rock to the back side - not the face side. This is counterintuitive but important.
I also built a fieldstone wall at the entrance to my laundromat. In that project, we poured a concrete footing and then layed the stones with morter. We finished by pouring concrete behind the stones and then brought the grade up to the top of the wall behind it. That wall isn't going anywhere. (See photo)
Larry