1) Rising a skeleton requires bones in the area or can be directly cast on a freshly slain enemy, exploding the flesh from the corpse to rise your minion. The level of skeleton is 1/3 your conjuration. It will pick up the weapon it uses in it's former life if that is still in it's possession. Uses relatively low mana, has a long timer, moves fast but has low Hp and damage.
2) Rising a zombie requires a corpse as the target to raise a zombie which moves slowly but has high Hp and damage. The level of zombie is 1/3 your conjuration. Uses relatively low mana and has a long timer.
3) Rising a ghost/wraith requires the finger bone of a slain enemy which can be looted from corpses. This will summon a Spector of level = formal life level x your conjuration level x 1%. Uses medium mana and has long timer.
4) Rising a bone horror requires multiple skeletons of atleast 3 humanoids or a giant. The level of the bone horror is 1/2 of your conjuration. It moves slowly but hits and tanks like a truck. Uses high mana and has long timer.
5) Rising a lich is not possible.
6) Summoning creatures from oblivion is as per normal and requires no components.