Everything starts with a Concept! It is very convenient now to use 3d software in concept art production pipeline. Usually it starts with a rough or detaild 3d blocks, separate 3d objects or even complete 3d scenes with later painover in Photoshop or other 2d image editor.
3DCoat is great for making 3d stuff for Concept Art.
Just watch these videos. They speak louder than words:
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