Warren has a unique grasp of space.  Not only to create the piece, but with an understanding of how it will be used.  His pieces are a permutation of the following: 

CLAY
Porcelain - During a short period, Warren worked in porcelain.
Stone - Has varied through the years.  Has always mixed his own through 2002.

SHAPE
Rounded -- given his use of the wheel, rounded is the predominant shape.  However, he occasionally would modify a rounded by one of the below methods.  I have yet to see any slab work, most was built on the wheel.
Squared -- Warren will take a rounded piece and simply square it.  Sometimes he may only square the neck, other times he may square the belly.  
Triangular -- A rounded piece is paddled or shaped with a triangular belly.  The foot and neck will typically remain round.
Inverted  -- One of my favorites.  Warren would play with the 'belly', instead, creating a 'barrel chest' where the volume of the piece was greater at the top instead of the bottom.
 

COLOR
Glazes - Shino, Matte Gray, Matte Brown, Temmoku, Salt, Yellow Ash, Dark Green, Dark Blue, White.

TEXTURE
Paddled
Sgraffito
Swipes
Fluted
Faceted/Cutting