...here's how I do them!
Bombshell mermaid image stamped with Black Memento ink as it doesn't smudge or run with Copics.
Skin colour- I start with an all over colouring of E00
Now imagining the light is coming from the right of the image (as you looks at it!) I place my shadows on the left and around any 'edges' say of clothing and hair etc.
So add E21in a thin band on the left of the image.
Now take E00 again and go over the colouring in small circles to blend the 2 colours together.
Take E02 and add colour in thinner bangs on the left of your image:
Finally for the skin I use my darkest shadow E11 in the smallest amount in the far left side of the image:
Here's a rough map of what I am doing:
Then once again I blend ALL over the skin with the E00 so the colours meld together!
I then use E21 for the darkest shadows which go FAR left:
I like to use a little R20 on the cheeks for blush and blend in again with E00 and I add a little eyeshadow something pale like BV02.
For a LONGER tutorial see my article on It's A Creative World!