Where all are the hooks defined in a contributed module?

Question

1. What are the files in which core hooks are implemented in a contributed module?

2. Are they declared in .inc files? If so, what are the naming conventions for those include files containing core hooks?

Answer 1

1. The convention is to park all core hook implementations in .module.
2. .inc files are used to break off different groups of code like custom class definitions & administration form handlers. Some have their own naming convention for contrib hook implementations (e.g. .views.inc, .rules.inc, etc.).