well, when you say terraining, what are you trying to make? an orderly city, natural chaotic kinds of terrain? different styles can be done differently. If you want to make a city, its usualy a good idea to make things symetrical and straight. If you are making like, random wilderness, I usualy like to start with grass, and make dirt and mud along traveled paths, placing different doodads on the different terrain types, like, place flowers along the grass and place rocks and pebbles in the mud. don't over do it with doodads either, too much makes it look congested.