What should go into an .h file?

Question

When dividing your code up into multiple files just what exactly should go into an .h file and what should go into a .cpp file?

Answer 1

Header (.h)

• Macros and includes needed for the interfaces (as few as possible)
• The declaration of the functions and classes
• Documentation of the interface
• Declaration of inline functions/methods, if any
• extern to global variables (if any)

Body (.cpp)

• Rest of macros and includes
• Include the header of the module
• Definition of functions and methods
• Global variables (if any)

As a rule of thumb, you put the "shared" part of the module on the .h (the part that other modules needs to be able to see) and the "not shared" part on the .cpp

PD: Yes, I've included global variables. I've used them some times and it's important not to define them on the headers, or you'll get a lot of modules, each defining its own variable.

EDIT: Modified after the comment of David