Blender 3.x: Correctly Using AO, Albedo, Normal, Metallic, Roughness Maps (2 minute tutorial) 

There are a few common mistakes to watch out for, but pretty straightforward once you've done it a few times.
The common mistakes are:
Ambient Occlusion: know when to use it and when to ignore it.
Non-Color vs sRGB: sRGB is used for albedo and AO, non-color is used for roughness, metallic, and normal.
Normal Map: You should have a Normal Map node between your normal map and the normal vector input on the shader, otherwise the results are incorrect (and the difference is visible).
3D models shown:
Post-Apocalyptic Phone Booth: sketchfab.com/...
Grand Piano: sketchfab.com/...