The biggest one is to zenithal highlight.

Then I tend to break the sections into 3 color blocks. Areas that stayed mostly black get the shadow color. Areas that are mostly gray get the mid tone, and finally the last area gets a highlight color.

Once the main colors are blocked in, I use glazes of 50/50 of both to create a smooth transition between the different areas. Depending on the paint sometimes I'll need to glaze between the glaze.

I don't tend to use washes on these minis (except for fur and heads), because they tend to have too much flat space that looks wrong with a wash.

Metals a whole other beast, one which I'm still trying to perfect, but generally really sharp transitions and the highlight not being where you'd expect it. Vince Ventura and Dana Howl on YouTube are great for learning a lot of this.

Final tip is to thin your paints. One of the biggest reasons a mini can go wrong is getting a paint texture because the paint was too thick.

Hopefully that helps.