I want to briefly cover the last three elements in the ‘Magic Formula’, that is

Contrast
Overlapping
Mix Media
Into the Picture
Texture
Cast Shadows

Into The Picture:
Avoid barriers in the ‘Eye Path’.  A gate left partly open or open is better than closed, when it forms part of the ‘Eye Path’.  The viewer should naturally want to stroll into the composition and wander about in it.  What is just around the corner?

Texture:
While I do not throw sand onto my paintings to make it look sandy, the principal of creating texture is good.  I love to render rocks for example, with bold impasto pallet knife work that mirrors the rocks texture. Do not over do it but definitely do it!  The texture of the image you are depicting should be obvious to the viewer.

Cast Shadows:
I have said much already about this.  Everything we see is in light.  Light is striking and spilling across it, therefore, choose a light direction and stay with it.  You should have ‘Highlights’ and ‘Catch Lights’ towards the light source, half tones, shadows, reflected lights and lastly cast shadows.  It should happen in this order

Highlight
Catch Light
Half Tone
Reflected Light
Cast Shadows

Try Painting a ball like that you will see what I am talking about.