Make sure you always have detect magic affecting your necromancer. Look at mobs before you kill them. Raise zombies from mobs that are hasted. A great first zombie is the scallywag near the storm giant village. Hasted, dirt kicks, disarms, shield disarms and berserks. Enjoy.
P.S.-You cannot animate any mob above level 52 (as a necromancer, it is possible as a different class however)