Now, I don't know all the science to it so I won't pretend I'm an expert but I do know it has a pH level closer to hair than shampoo. Shampoo strips your hair of the natural oils that are healthy for it, so over time it trains your hair to produce more and more oil causing more oily hair. Since baking soda is close in pH to your hair it doesn't cause it to over produce those oils. 1/2 cup to 1/3 cup is all you need. Make a paste before hand or just grab it as you go since it'll mix in either way with the water and you're good to go. It doesn't produce a comforting lather that chemical products do, but that's one luxury I can part with. Also you will have to wash more frequently for a while as your hair gets retrained to produce its natural oils at the right level.
For conditioner there's another very simple solution. Apple cider vinegar. Crazy I know! I'm not gonna lie to you, my hair has never been softer. Like the baking soda there's a loss to luxury. Since it doesn't have the waxy coating other chemical conditioners have so your hair isn't silky smooth while wet. When it dries though, omg. I love running my fingers through it! 2-3 tablespoons in about 8oz cup of water is all you need. I soak my ends for about a minute in the cup then pour the rest over the remaining hair. After that you just rinse!
I know some of you might call this crazy, but I won't go back to shampoo. I'm loving my hair now, and its without chemical crap.