modding - How do I add a custom mob to Minecraft?

Basically decided to make my own mob, I have:

• Created my mob's entity class


• Created my mobs model class


• Drawn the model


• Added the function call for addMapping within the EntityList class

I'm stuck on what to do next. I've tried finding the code that deals with passive animal spawning in the world, however I can't seem to find it.

Help greatly appreciated.