I have been using baking soda as my shampoo and underarm deodorant for some time now. I have not used commercial shampoo for about a year and commercial antiperspirant for about 6 months. I switched to a healthier, greener and cheaper option...baking soda.
I use baking soda and water as my shampoo. My best guesstimate for the mixture is about 1 part baking soda to 6 parts water, I place the liquid in a bottle and when I take a shower I give the bottle a shake, pour some on my hair and gently massage my scalp for a minute or two. I end up with clean, shiny, soft hair.
Now for the deodorant, I use straight baking soda that I place in a salt shaker. I shake some baking soda in my hand and lightly rub my underarm with it. If you have sensitive skin you might want to cut the baking soda with some corn starch. Start with a fifty fifty ratio of baking soda and corn starch and increase or decrease each as it suits.
Just remember that the baking soda does not stop your body from sweating, it just stops the odor, it's really quite amazing.