In my world magical abilities are inborn.
To access that ability, mental techniques are required to receive a certain result. Sometimes this involves rituals, sometimes just a cleansing breath.
A persons affinity with a particular kind of magic (in my world white, black, elemental, or necromantic) depends on which supernatural element they access first. In my necromancers case, he brings his father back from death after a heart attack in a field of wheat. As a result of bringing the father back, the wheat (and all the living things around them, are sucked of their life force. Since he used his magical ability to deny death, he forever after has one foot in the world of the dead.
He has the power to animate anything that had been alive. He can communicate spirits that haven't yet, or have no desire to, move on. More importantly he can feed power to spirits and animated skeletons and they like, but always at a cost to something living. The self aware the living creature he's trying to take power from, the harder it is.
There's a lot more, but this is the basics of necromancy in my story.