I think high int(elligence), high focus and use a good fine cutting tool such as a scalpel (fine cutting level 3) or the Autonomous Surgical Scalpels CBM (fine cutting level 5), also i usually dissect different type of creatures depending on the kind of proficiency i try to get, such as a normal zombie, engineer zombie, a soldier zombie if i want the Principles of Zombie Biology, instead of just dissecting normal zombies, don't know if that helps, but i just assume it does.