For my painting The Superover I was looking for mostly diagonal lines because I needed to create a great sense of movement. I found them in the legs and arms as well as putting them in the background with diagonal strokes around the moving parts. I needed some stability so got that from the horizontal line of the back arm. In the original photo that back arm is slightly tilted but I kept it straight to provide that anchor and contrast between everything else moving.
I wanted a good curve as well to put depth in the painting and make the viewer think the figure was coming towards us, I found that in the curve of shoulders. I couldn't really find any other curves but would have liked at least one more.
These lines I worked at keeping throughout the whole painting, from the underpainting to the colour. The back arm has probably been the most effective line in this painting almost pulling us back from the surge forward.