Well, it’s pretty hard to describe a modeling process by text. The best thing we can do is point it at the right tutorial so you can learn to model. I guess Sessions is a good one:
https://cgcookie.com/courses/sessions-minimalism
https://cgcookie.com/courses/sessions-macro
And maybe the Pokeball has concepts that will help you with it as well?
https://cgcookie.com/courses/catch-creating-a-pokeball-in-blender
