Substance Designer Community Wiki
THE PBR GUIDE BY ALLEGORITHMIC - Wes Mcdermott
Physically Based Rendering Encyclopedia
PBR Texture Conversion | Marmoset
The Anatomy of a Perfect Video Game Material
For basic tutorials look here or alternatively refer to the Resources section
I am going to make mostly references to a PBR realistic style of Designing but these practices will follow through to most methods.
Try and think about the location of your material, think about the surface detail and the order it is naturally built up.
If you are looking for more details on uses for individual nodes look here