First I think you should have used the search button because this site has lots of guides about leveling pets/chars like darkdeaver's or kojika's.
http://wlodb.com/topics/4645
http://wlodb.com/topics/13527
So far I think the best place to train him is Pine forest but not at the 40+ cirrus because then the Eq/Armlets will destroy so try to stay away from them.From what I know fred has a decent amount of hp so it won't be so hard to train him there.