Firstly, I open a new .psd file in Photoshop. It will be vertical, and the resolution will be 150-200 ppi. I generally start with a lower resolution and ramp it up later when I’m detailing the illustration, enabling me to work faster and smoother. I create a textured background before starting to draw, so I get rid of the white background. I open a new layer and start to sketch with some thin brushes, as though drawing with a sharpened pencil. I don’t need to put a lot of detail into this stage, just define the general silhouette and lines (Fig.01).
LINK:
http://www.3dtotal.com/team/Tutorials_3/makingof_alien_priest/alien_priest_01.asp