A series of face practices, as it's something I seem to have been avoiding a bit too much recently!
Shape and colour study. Trying to not worry about the shadows and the volumes as much, just getting the main shapes and features to look good together.
Sketching and painting busts. Actually removing all the colour information helped me focus on getting the planes looking right and making the shapes work together well.
Mixing the bust sculpting studies with the colour studies. Trying to create the same simple planes but with the warmth of skin tones!