Great start! Shading is relatively easy: choose a base colour, give it highlights, and shadows. This works best and easiest if you choose the middle of 3 available shades > middle is base colour, top one is shadow, and bottom one is highlights. When dealing with very light colours, white can be used as ultimate highlights. And when dealing with dark colours, black can be used as extra shadow. Then it's just a question of layering the "smokey" bits. :)
