Hi @fanaticmonkey, welcome to the forums! 
Here are some resources for working with quadrupeds, from skeleton to muscles to tails.
Skeleton
Applying physics to the underlying skeleton/rig, for e.g. falling over or getting hit by something.
Muscles
Some general tips on how to achieve muscles.
Ears, Tails, Cloth
Relates to cloth, which is a step up from a tail or ear, but the techniques are the same.
Hope it helps! If you post your progress, we’ll be able to guide you through your setup and provide feedback too.