Character Guide: http://media.steampowered.com/apps/dota2/workshop/Dota2CharacterArtGuide.pdf
Every character artist needs to check that pdf out.
Texture Guide: http://media.steampowered.com/apps/dota2/workshop/Dota2CharacterTextureGuide.pdf
Its a compilation of some of the most valuable points we as character artists can EVER EVER hope to master.
SOooooo valuable for them to compile this stuff and put it out there for free