Your preferred C/C++ header policy for big projects?

When working on a big C/C++ project, do you have some specific rules regarding the #include within source or header files?

For instance, we can imagine to follow one of these two excessive rules:

1. #include are forbidden in .h files; it is up to each .c file to include all the headers it needs
2. Each .h file should include all its dependancies, i.e. it should be able to compile alone without any error.

I suppose there is trade-off in between for any project, but what is yours? Do you have more specific rules? Or any link that argues for any of the solutions?