When I ride, I wobble. Well, I mean the wheel wobbles from side to side. As I'm riding I don't think the wheel is moving all that much, but the tracks in the damp dirt of the trail don't lie. On a return ride a couple of days ago my wheel and Karen's bike wheels were side by side on the trail, and there was a huge difference. Bike wheel tracks were straight while the unicycle wheel track looked like a snake.
A simple, but fun, drill I've tried during the last several riding sessions has been to ride a defined line. The straight and curved painted lines on the basketball court where I've been practicing figure 8s have been good for this exercise. I try to keep the wheel straight on the line without much side to side movement, particularly at slow speeds. I find that if I concentrate on spot about 6-8 feet in front of me and try to head for that spot, I can stay on the line. I'm sure there is still wobble just due to the way pedal force is applied to the wheel.
On the way to and from the court is a two-block stretch of singletrack alongside a golf course. The singletrack is where the sidewalk should be. It sometimes disintegrates into rutty turf, but for most of the length is a 6" dirt path. I find that path hard to stay on for the whole distance, particularly where I need to slide between a street sign and a steel berm. Doing the line drills on the court, though, seems to have helped. Yesterday I made my first pass through that track without a dismount. Next, I'm interested to see whether it has made a difference on the gateway trail horse paths. Maybe if I ride a straighter line I'll be better able to apply more force to the wheel with better balance and make it up those hills.