I don't really have a concept for my textures. Mostly I only know what coloring I want.
I mostly use Photoshop's brushes, and one of Vered's brushes for textures and experiment a lot with filters and blend modes. And I use levels and curves adjustment layers, loooots of them (it's what makes them look shiny).
Sorry I can't be more specific, it's really trial and error most of the time.
Oh yes, and I always make one large texture and crop it for these sets.