Potatoes of any size should be firm, relatively smooth, clean, reasonably well shaped, not badly cut, bruised or skinned, nor should they show any green from light burn.  They should not be wilted or show sprouts.  Cooking quality varies from variety and growing area.  For Baking and french fries potatoes with high dry matter content perform best while potatoes for boiling or poaching for salads etc, should have a high moisture content..  The Russet from the north west tends to be a drier potato and has a reputation for good quality baking.  early or new potatoes are considered to be high in moisture and best used for boiling, salads, and steaming.