I believe such a guide/tip list should be made so that the people who wish to make these maps know what the guide lines are and where to start when making said maps.I will start this Guide or List of Tips with my suggestions.
1.The map must be even between humans and zombies
No ventilation connecting every room in the map including both spawns
No large caches of barricade gun ammo
No ways to glitch out of the map this gets annoying for zombies when it is impossible to find humans
No wood only props,non destroyable props,only metal props