For a long time, I did not use the nodes window. I stuck with the features I understood from using Terragen 0.9xx. The basic way to build a landscape is to think of it like a cake. The base is the bedrock layer. Next comes the exposed stone layer; I use slope constraint in the surface layers. Now the sand/dirt layer, slope constrained. The grass layer, slope constrained. Last the snow layer (if I want snow).
This way gives you a basic landscape to start adding things to. Power fractals into the color input fro instance, provide more variation. Altitude settings in the Surface layer can keep a grass layer from 'growing' into the water.
I hope this helps.