One of the useful things I have learnt on the course I’m currently taking at QU is to do a value study before you start to think about a colour scheme. One of the exercises was to draw a simple landscape and then shade it in all the combinations of high, mid and low values. I used SketchBook Express from Autodesk to make my studies. We have recently acquired it from the Mac App Store. It is a very simple tool that you can use intuitively – great for these sort of exercises, where you just want to get on with the task in hand and not fight with the software.
It is interesting to see just how a different value scheme can affect the look of the sketch.