Good practices for setting up include files are key to keeping large code-bases manageable, in pre-modules C++, and this article presents 15 rules to keep you on the right track.

C/C++ Include Guidelines

by Thomas Young

From the article:

The rules listed here are relatively mechanical, by which I mean that these are things that can be applied locally to individual bits of source code, without strokes of genius or flashes of inspiration, but with the possibility to nevertheless significantly improve code organisation, which is useful particularly in the case of large legacy code bases.