We began a monochrome value study in class, which, with a little analysis we decided needed more than three values (layers). Since a study is usually meant to be an over-simplification, we chose to limit the range to just 5 layers; white, light grey, middle grey, dark grey and black. The value scale you're making will be helpful as a tool for deciding which value to assign to a given shape.
Part of the purpose of a value study is to make sure you're taking advantage of relative dark and light as a means of separating adjacent shapes that are meant to be in different spatial planes. When you assess your finished study, look for any areas where the space seems ambiguous. Consider whether the addition of color will solve the problem, and if not, imagine adjusting the values.
The assessment of the finished study is the most important part of the process, so be sure to squeeze all the information you can from the little piece of paper, and write your notes and arrows directly on it. Ask where there are areas that require greater subtlety or specificity. Are the darks dark enough? Have you reserved lights as needed? Since the studies we've done so far are all hard-edged, think about where a soft edge may be helpful.
When you have answers to your questions, get a good piece of paper and start a proper painting by blocking in the major shapes. They're the ones that need to appear separated in space. Outlining them should be all the drawing you need. At this point, we don't even need to know what they are, just where they are. For each shape, look for a way to make an overall wash - a kind of common denominator - that can underlie everything that will come later. If you're moved to continue to the second layer, put the first try aside and start a second on another sheet, so we can see what your first layer looked like all by itself.