There are different theories surrounding how many times men should shampoo their hair. While some say that it should only be once a week, others recommend thrice a week. But the ideal way of deciding how many times you need to shampoo your hair in a week is to see the requirement according to your hair type.
While men with short hair can easily do with shampooing twice a week, those who have longer mane should go for three times a week simply because longer hair requires more moisturizing and care. If your hair is dry and puffy, then you might want to keep them properly conditioned with regular shampooing and conditioning three times a week.
If you are more exposed to dust and pollution with an outdoor job, then washing them on a more regular basis is the best bet to keep your healthy. Just make sure that you are not over doing it as too much use of shampoo can also dry your scalp resulting in hair fall and hair damage.
The best way to keep a check on the number is to keep a check on how your hair feels. If they are dry, sticky or no way near being soft, then you need to shampoo.
Different hair types would require different kind of care. And keeping a check on how they feel on your hands when you run them through your hair will give you a fairly good idea.