Additive effects are kind of the way my mind works when it comes to layering. I can't layer in my head. Sure, I know my own wardrobe so well that in my head I could try and put things together like Cher's computerized closet (Clueless, anyone?) but when it comes to layering pieces of my wardrobe other than top+bottoms, it's really just trial and error.
It goes something like this: stand in closet, pick one piece I want to wear and everything else must work around. Rifle through hanging clothes for vests, sweaters, tunics, jackets--anything that will work. Then: smaller layering piece, like belt or scarf. Then: shoes. Then: bag. Then: lipstick color (since by the time I shoot my outfit it will be worn off anyway).
I really wish there was more method to my madness but it appears I just don't operate that way!
One new hair trick I'm loving: messy bed head. Spray bumble + bumble surf spray in towel-dried hair, then air dry hair. Scrunch is up when it's fully dry. Done!