For me: Painting merely is taking an image you already have, whether it is what you see with your eyes or what is in your mind, flattening it down and copying it as best you can on a canvas, either digital or analogue.
It starts with identifying the most basic shapes in the image and then working to build up the rest...
The perspective, lighting and depth is built up until it looks good enough to say, I am happy with this.
One of my favourite images summarizes the process I use, called 'how to draw an owl'.
Step One: Draw Circles.
Step Two: Draw the rest of the Owl.
http://vocaroo.com/?media=vAnK4Exs9bDCJuL5G
It's a little less of a jump than that for me.
I work by outline as opposed to framework it with circles and polygons.
Sometimes I will use a framework, but I mimic the image in my head for the most part.
It's basic shape, Blocking the dark and light areas, adding highlights and dark zones.
Once I got that blocked out, I can basically see how it looks from there.
Just fixing from then until I have my image.