Each person will have a different learning curve, but I think I can offer some tips that many will find useful. By way of background, I did ride a unicycle when I was 13 year old, but that was 50 years ago and I don't think it helped with the Solowheeling at all. At 63 years old, I took very measured and deliberate steps in learning, and I believe that's the way to go. I cannot believe folks I see on YouTube trying to do freestanding starts outdoors the first time on the wheel. I saved the freestanding starts for MUCH later in my learning program. First, I learned the basics indoors in a hallway. I do not have the training wheels, and I would not recommend them, they seem to be counterproductive to learning proper technique for painless, enjoyable, easy riding. To start, I stood stationary on the wheel between two highback chairs and got used to moving back and forth a couple inches, just getting comfortable on the wheel and with some motion. (Of course, the power must be on before you attempt to stand even stationary.) I then tried starting forward and did a lot of 2 ft rides with shifting legs right and left to correct. Then I had an epiphany and picked up the key to managing the wheel. It's a "Zen" thing -- from the stationary position between two chairs, stand up straight, look at a point about 15 foot in the distance (like a wall straight ahead with two more chairs set up as your finish point) then just relax and think "move to that point", and the wheel will take you there. Don't worry about going too fast into the wall, you will intuitively slow down. I had a door jamb (with no door) midway in my 15 ft practice path, and practiced slowing and stopping within the jamb, just holding out my hands there, and starting again. Of course, the runs were not perfect, but within 30 minutes or so I was doing reasonably controlled straight runs back and forth. I practiced a total of a couple hours over a few days within these limitiations. I thought I was pretty comfortable and went out to a bike path, starting from a stationary standstill by using a pole. Turns out I wasn't really ready for this, it's a whole different experience outside with nothing at all nearby, and very intimidating. After about a one half scary mile I ended up gaining speed, and trying to slow down (unsucessfully). It didn't seem to want to slow down even though I was consiously trying to lean back. I was pretty much riding atop a runaway wheel. Did a full forward dive to the pavement when I exceeded the maximum speed. I had tried too much, too fast. I sprained my right hand pretty severely and could not even think of getting on the wheel again for about 3 weeks, as I couldn't risk further damaging an unhealed wrist/hand. I then decided to take the following measured steps, very successfully. First, I got some rollerblading wrist guards for security. I practiced a bit more indoors while healing, staight line hallway stuff just to get used to moving on the wheel. Ready to advance, I went to a fenced in tennis court area (3 courts surrounded by one high chain link fence. I would then just get set up along one side with my stationary start by holding the chain link fence with one hand. Then just remembering to use the "look at the point you want to go to" and think "wheel, take me there, remembering to stand very straight, and glide 30 ft or so to the chain link fence staight head, and holding on there, turning 90 degrees releasing and going to the next corner. After 15 minutes of just riding the perimeter of the fence in area, stopping at each corner and manually turning, I added one shallow 90 degree curve without stopping. Just kept advancing slowly until I could do all four turns around the courts in one large oval. At this point I was using my arms outstretched in various positions to help with the turns, and even on the straight runs. As you get more experience, you'll find the arms come down. Practice your speed control changing your speed between corners as you go straight toward the opposite chain link fence, grabbing it only after you stop a foot or so in front of it. The first time out on the tennis courts I did about 30 minutes just practicing the straight line runs and then the shallow turns. Next time out I found another set of five courts surrounded by the same type fence and went there several days in a row practicing about 30-45 minutes at a time, doing little drills changing up right and left turns, and eventually zig-zagging between the five courts doing 90 degree turns. I had about 5 wheel hours at this point, and was feeling pretty good. Went out into the school parking lot and surrounding sidewalks where the tennis courts were and found that switching from smooth tennis courts to real world bumps is a whole next step. The first small sidewalk crack bumped me off but still on my feet. I was really disappointed, since I had been doing so well. Turns out, you just need experience to handle the bumps. But get really good on the smooth surfaces before you move on. I moved on by going to a nearby college campus full of long smooth sidewalks (like 1/4 mile runs) and lots of criss crossing diagonal sidewalks to allow choosing 45 degree turns, 90 degree turns, and 135 degree turns (later on), as well as small ramps (the handicap ramps to buildings). At this point I still had not mastered the "freestanding start", still using a pole, or rail, or sign to start out. By going to two different campuses for about an hour each time out I gradually got more and more at ease. In a one hour outing I might get bumped off on a crack or uneven surface once or twice, but would land on my feet. I only hit the ground falling forward one time after that initial disaster with the sprained wrist, and my wristguards prevented injury on that 2nd fall. That fall was when I was attempting a pretty good bump on a driveway cutout, just to see if the wheel could do it. It couldn't. One of the campuses had a nice run of building support poles about 10 feet apart, and I learned to slalom turn on those, and gained a lot of confidence. Campuses have lots of large circle opportunities around planters and fountains and food court areas, they're usually people free early evening, too. They also have large plazas with patterns in the concrete work that allow you to make up your own zig-zag drills. I never had need for the shinguards, although I did have a very slight bruising on the shins in the tennis court training period. Nothing painful, for sure. As you progress, you hardly notice any pressure on your shins. I did use hiking boots with full ankle coverage, and I recommend those until you're really getting good.
Only after you have a very nice controlled freestanding "stop" -- basically coming to a full stop and then just stepping one foot down with no drama-- should you THEN try to learn the free standing start. It's pretty much the opposite of the no drama stop. If you delay the freestanding start learning until you are really comfortable with every other aspect of riding, you'll find it much easier. It's not that necessary anyway, since there is almost always a car, a railing, a sign, or even a friendly shoulder to mount your wheel for a start from stationary position. This allows you to get your feet in exactly the right position, as well. It's tricky riding if your feet are not exactly where they should be.
I never used the training strap after my first unsuccessful time out. I think it really messes you up, restricts your arm balancing (needed early on) and also can lead to unproductive riding habits. The wheel isn't going anywhere if you do get bumped off, it turns itself off. In fact, with the strap holding the wheel upright you prevent it from shuting off when you're bumped off. The wheel will take getting bounced around on the ground with nothing more than scratches. You shouldn't be riding in crowds until you're far enough in your training. Until you gain some experience, you might want to put some duct tape on it to prevent scratches. You won't need it taped up for long.
OBSERVATIONS and TIPS: Progress is slow, but steady. The fun factor increases with experience. My first many hours on the wheel (even though I was doing pretty well) my heart would be racing when I finished my practicing. Eventually you will become relaxed. Your arms will come in to your body, even to your pockets. You will automatically pick up the leaning turns, and the slow speed sharp turns. Make drills for yourself. On a bike path with a dashed dividing line I gained lots of experience quickly by slaloming between the dashes. Make up drills for yourself, just going straight is useful, but you can speed up your leaning curve by finding a place like a campus with mult-turn opportunities. One thing I found uncomfortable is the inability to keep my speed down when I would have a straight run with nothing ahead of me. Riding near the maximum, you get the kick back warning where the wheel pushes you back a bit. It's kind of unnerving. When there is nothing but clear path ahead, though, it is natural to keep speeding up. I finally realized I can avoid this by simply turning my head 45 degrees or so looking at the side view, you automaticly slow down enough to avoid the push back. The other thing you can do (should have mentioned this earlier on) if you find yourself going to fast with an open road, is to look at a specific mark on the path ahead and just "will" yourself to stop or slow down by that point. Again, it's the Zen thing.
Other key points to remember at all points in your training--always make sure your back is straight. Your knees should be locked straight as well, although until you get more experience just try to keep them as straight as possible.
Watch all the YouTube videos, I went over and over them while I recovered from my sprained wrist, and I think it helped.
OH YEAH -- IMPORTANT!!! -- Always be sure to check your tire pressure! For learning you want to keep it around 35 PSI. If you weigh more than average, up that to 40 PSI. I weigh 180 lbs (6ft 4") and keep the pressure just over 40. You may lose a pound or so of pressure each day with the wheel just sitting, it's normal. Higher pressure will be a bit more bouncy on the bumps, but will actually help you with them and, more importantly, increase your distance on a charge and increase your manuverability.
Also, your wheel will lose charge just sitting a few days. Top up the charge just before you ride, if possible.
I'm really enjoying my wheel at this point. I've got a total of around a dozen hours on it, spread out over as many weeks (remember, I had a 3 week down time for injury). I still need to refine my freestanding starts, just haven't put too much work into them. It's amazing how precise you can be, riding around pedestrians on a bike path or sidwalks is pretty easy once you've got some time under your belt. I live near Niagara Falls NY, and buzzing around the state park there is a real kick. Solowheeling is perfect for sightseeing in large parks, since you can cover so much distance so easily. I look forward to using it when visiting other tourist areas (Gettysburg, DC, etc).
I usually ride out a full charge, which is about one hour, or about 6-7 miles. I think 7 miles is about maximum for a 180 pounder.
If you're still with me at this point, I hope you'll consider trying some of my methods. I hope that if you've been intimidated by the horror stories here and some of the YouTube videos, that it helps you to know that by taking measured steps in a progressive learning schedule you can learn to enjoy your wheel like a pro in a reasonable timewithout inflicting a lot of pain on yourself. If anybody is in the Buffalo New York area, let me know -- it would be a lot of fun riding with another Solowheeler.