As in no shampoo. Here is a quick how-to, and here is an NPR piece on it. (How I miss Day to Day!!!) I have done this before with great sucess when I lived in California (and had glorious long hair, kissed golden by the sun). I didn't water down my apple cider vinegar, and I put the baking soda on dry. It really really worked.
Did not do so well in Indiana. I had to switch to either Head and Shoulders or Coal Tar shampoo (I varied which one I used). I kept doing the apple cider vinegar rinse, but otherwise I had to use shampoo.
Now here I am in Wales and unless I use the nasty coal tar shampoo, I itch like crazy. I have tried the baking soda and cider vinegar thing but it doesn't seem to work like it did in San Diego. Today I'm back to itching like crazy and I have to wash my hair (even though it looks clean). I am out of cider vinegar, so I'll use lemon juice. Since it doesn't seem to rinse out as well as I'd like, I'm going to use plain salt instead of baking soda.
I know you are all on the edge of your seats now.
I'll keep you posted.