I always start with an oil primed linen canvas.  I cover it with a ground color mixed by using raw umber, a little ultramarine blue, titanium white and some gamsol.  It is possible to use artist’s turpenoid if you do not need the canvas to dry in a hurry.  Spread this with a bristle brush and then wipe down with viva paper towels until you achieve a neutral grey of mid value.  You may use other colors if you wish.  (For example, I am using a mix of Indian Yellow and Winsor Lemon Yellow for a still life which has a lot of gold tone in it.)

After this is dry, transfer your refined and completed sketch to the canvas.  The old masters called this sketch a cartoon and used to transfer it by punching holes on the major outlines, then daubing it with charcoal dust.  There are many ways to transfer your sketch but my major piece of advice is to work out all the problems in your sketch  before you move on to the next stage.