I went to the companions guild for the first time and asked them to let me join their guild. I went to start the initiation which was to show him i can fight outside in the training courtyard. After i battled him he told me to do something else I forgot. but after that part of the initiation i attacked him. Him and Eorlund Gray-Mane came after me. Heres the part where you can level conjuration FAST:

Let Eorlund Gray-mane attack you once, then cast Bound Sword. You will gain a Conjuration level because it is glitched. Unsheath Bound sword then cast it again. Keep doing it till you reach your desired level. Sometimes it will stop leveling your conjuration. But don't worry, all you have to do is let eorlund attack you again and you will gain conjuration levels again.

P.S don't attack eorlund, just keep walking around him and cast bound sword.

Same thing works with slaughter fish. - attract one or more, stand on land so they can't attack and cast bound sword. No annoying bounties

Don't know if it's been 'fixed' but it was also possible to get the soul trap spell and cast it repeatedly on a dead beastie or baddie.