1. Keep your sharpening stone flat!
This may seem obvious but it's often overlooked by many people. Trying to sharpen your knife with a concave stone will make it nearly impossible to hold your knife at a consistent angle and will not result in a sharp edge. To check if your stone is completely flat, mark your stone with a pencil and move your stone fixer back and forth with some force over it until the marks are gone. If your stone is even slightly concave you will see that the marks in the center will not disappear until it is completely flat.
2. Round out the edges of your sharpening stone
This process is called kado-otoshi and it is to prevent your stone and blade from chipping when you use too much pressure.
3. Always hold your knife at four points
This is to help you hold your knife at a steady, consistent angle while sharpening. Your main hand should firmly keep the knife stable while your other hand just acts as a guide.
4. Use a sharpening guide
If you are new to sharpening, you may want to use a sharpening guide. Once you get a feel for the angle, you can stop using it.
View Super Togeru Sharpening Guide
5. Steels do not sharpen knives
One thing you should keep in mind is that a steel only maintains and realigns the edge but doesn't actually sharpen it. If you want to sharpen a knife, use a sharpening stone, and to unfold the burrs, use a steel. A steel can never replace a sharpening stone.