I'll copy from the CoolMiniorNot painting guide (shortened):
Start with a midtone of the final look you want to achieve (this is the base color between the highlights and the shaded areas).
Then add a wash of either the same color or a darker color to add shading to the areas where light wouldn't reach (base of his hair etc).
Start building up the shades with your original color, applied to the raised areas. This first "highlight" is applied to a fairly large area.
The second highlight is a bit lighter than the last, and applied to an area that is smaller (by smaller, I mean closer to the ridges and raised areas of the model). You are probably done herebut a third highlight can be added if you like, just made it lighter and on the very fine edges of the raised area.
Their example is ultramarines blue as the base, a blue wash then UM blue as first shade, UM blue with a bit of skull white second and a mix with even more white third.
Hopefully that helped. Also please do a psyker from DBZ.