For all vertical positions do the best that you can to keep your palm facing outwards.
(This is not quite possible in position C.)
For positions a and c point your fingers forwards. For b and d your fingers point back.
As with the horizontal positions, reach your elbow away from your ribcage, and make your fingers feel long.
In addition, make your neck feel long by pulling your head back and up and keep the front of your chest open.
Work towards keeping your side and back ribs lifted slightly so that the sides and backs of your torso (as well as your neck) feel “long.”