I work on a flat table - my table is my palette. With all the visual distraction around the painting, it's hard for me to see how the painting's coming along!
To determine the progress of a painting I'm working on, I find it useful to place a mat over it. The mat isolates the painting from the surrounding area. If no mat is available, place the painting on a larger sheet of white paper. It gives the illusion of a mat and has the same effect.
For larger paintings on canvas or paper, I hang them on my studio wall. This removes the work from the visual distraction of where I painted it. Just like a discarded mat, hanging my painting on the studio wall allows me to "see!"
Click HERE to view BobBlast issue 44
"Isolate Your Painting" video.