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

in addition to all other answers, i will tell you what you DON'T place in a header file:
using declaration (the most common being using namespace std;) should not appear in a header file because they pollute the namespace of the source file in which it is included.