Lastly there is Conjuration . This series covers the pet summonings, darkness and disease series of spells. It is probably the second most popular specialisation for Necros after Alteration. I would recommend going with Alteration myself since you will use these spells as a Necromancer more than any other. Cleric Clerics only have 2 real choices of specialisation, Alteration and Evocation .
Alteration is by far the most popular choice.
It covers heals, cures, roots, and res spells. This means you'll have more heals, and be able to channel heals through on a more consistent basis. It will also reduce the mana cost of those expensive ressurection spells. Evocation is a choice that many clerics attempting to solo decide to go for. All the cleric direct damage spells are Evocation, this will allow more nukes for you mana, which is critical as your spells aren't very mana effecient in the first place.