In spite there are no basic techniques, some elements have past from master to apprentice.

As any kind of sorcerer, necromancers many times have invented their own rituals. The most common objects (but not always essentials)  used in these rituals were bones, hair and other parts of animals or even humans. 

Among the necromantic virtues we find: invocation of dead, curses, healing spells, divination e.t.c.