Not sure about other alliances, but this works on Daggerfall Covenant, it's what I used. Using this method I got to Werewolf Rank 10 within 2 hours.
Requirements:
- Full Lycanthropy (Obviously)
- 1 Skill Point
The target is those black wolves, they have a special ability that calls 2 smaller wolves that die with one hit.
These small wolves will fill your Werewolf Transformation Ultimate faster than any other enemy.
A few small wolves should fill Ultimate. You then run around the area killing those enemies, and it will quickly raise your level.
Once you hit Werewolf Level 5 (Or 6, not sure) you can get the Devour perk.
This perk will let you feed off of dead creatures to get more time as a Werewolf.
If you select the option to devour repeatedly and slightly move around the prey, you can gain more time without actually consuming the creature. This will essentially let you stay in Werewolf mode for an infinite amount of time as long as there is prey to use Devour on.
Locations:
Daggerfall Covenant
Level 1 - 32 can use a fort slightly to the right of Shornhelm, Rivenspire. It has a circular track with plenty of wolves on it.
Level 32+ can use other areas with higher level wolves or similar creatures (jackals).
I've found spots in Alik'r Desert that spawn Jackals with the same ability and spots in Bangkorai with the same wolves, but higher level.
Aldmeri Dominion
Unknown
Ebonheart Pact
Unknown
With this you can get to Werewolf Level 10 within a few hours.
This has helped me and many other friends, enjoy.