How can I learn to sharpen my Japanese knives properly?
The Japanese Knife Company has a couple of good tutorials on their website. http://www.japaneseknifecompany.com/sharpening-guides .

Update from Joe: 

They have videos on many different ways of sharpening knives (diamond steel, wheel, water wheel, stone, water stone, single sided blades).  If you check their YouTube channel Japanese Knife Company, they also have videos for maintenance of your knives (stropping using newspaper), storage (magnets or blade up in knife blocks; advantages of different blade protectors)

It's almost impossible to describe the process only with text, especially as some of his advice has to do with the sound of the sharpening or stropping, or showing undesired movements of your arm, so videos are the best way to explain the process online.  But even with that, you might not be aware of mistakes that you're making, so you may want to look to see if there are knife or kitchenware stores in your area that offer classes.