Method 1 - Soul Trap

The following is an easy way to get your conjuration skill to 100. In order to do this you need the spell Soul Trap, which can be bought for roughly 250-300 gold from Farengar Secret-Fire at Dragonsreach or Phinis Gestor at the College of Winterhold.Once you have the soul trap, find and kill an enemy and take them to a safe location. Once there just keep casting soul trap on them to your heart's desire, remembering to wait an hour everytime you run out of magicka to speed up the process, because even though the spell might not work it still counts towards the conjuration skill. You'll be at skill level 100 in no time!