FIVE. Not taking vitamins- In my opinion, this is the biggest hair faux pas. You HAVE to take vitamins to give your hair a fighting chance. OR. You have to take in enough veggies/fruits and natural vitamins that you don’t need synthetic ones. This would be fine as well. Biotin, Vitamin B12, Niacin, Vitamin C, Vitamin E and MSM (Methylsulfonylmethane) are all vital nutrients to keep your hair healthy and avoid dry, brittle locks. Image from Amazon.