Duckman, there a couple of ways of approaching panel shading:
1 Pre-shading.
This is where you apply a dark colour along the panel lines, before applying the top colour. It is then a question of building up the top coat so that some of the darker colouring shows through around the edges of the panel, leaving the centre of each panel in the base colour.
This works better on lighter colours in my experience, as the 'shading' effect is often lost under darker colours.
2 Post Shading
Essentially you paint the model as per normal, then when complete apply either a slightly darker shade of the base coat along the panel lines, or a very dilute mix of a colour such as Tamiya Smoke along the panel edges, thus just tinting the base coat.
A further refinement of this technique is applying a slightly lighter shade of the base colour to the centre of each panel, thus giving it a slightly faded look.
I've had good results with both techniques, and there is no reason not to combine both approaches in the one build.
Hope this helps.
Karl