It seems as though the clotting cascade is something you can study over and over again and it never sticks.

The important things to know are:

HEPARIN affects factor VIII in the INTRINSIC pathway and this is measured using PTT (partial thromboplastin time)
WARFARIN affects the vitamin K dependent synthesis of some clotting factors (purple in the image), particularly factor VII in the EXTRINSIC pathway and this is measured using PT (prothombin time) or INR (International Normalized Ratio, which is derived from the PT)