The word necromancy derives from the word nekros, dead; and manteia meaning divination and involves the communication with the deceased - either by ceremonial methods or by more simpler means.
In the past there were misconceptions about necromancy as there are today. One of them being that nigromancy and necromancy are the same and this is not the case. Nigromancy involved divination with black colored water, while like I said earlier, necromancy is divination with the dead.
One way to use necromancy is to ask the dead for the assistance of finding a lost object. The dead know more things that we do because they are not bound to the physical reality we live in no more.
Another strong fact that I would like to bring up is that necromancy does not involved reanimating corpses or controlling the dead. This practice is about getting information on certain problems that people are not likely to get while being alive and to commune with the dead.
Many people think necromancy is an evil practice, which it isn't. In the middle ages their were grimoires that were about necromancy and many people who practiced it believed in the christian God and even used his power in their practices.
Necromancy can come in many shapes and sizes as well. It is a jack of all trades practice because most types of divination can be used to contact the dead. An example is cartomancy, or using cards for divination. People can use tarot or even oracle cards to depict what the dead are trying to say. Another method could be casting lots or a simple pendulum reading.
As far as religion goes, you can be any type to do this practice. Necromancy is very much like witchcraft and is not a religion, but a practice. Shape and mold it to your desires, as long as if your don't try to dig up grandma and resurrect her dead body, go with it.
Not unheard of, but dead animals could also be a part of necromancy. Some people like to have a link to the dead and since human bones are hard to get, many people like to use animal bones and skulls.I personally love this type of practice because I like animals and I love collecting bones.
I hope this thread informed you on the practice of necromancy and made you a little wiser about it as well. If you have any burning questions, please feel free to message me.
Thank you and have a good day!