How Often Should I Wash My Hair?

There is really no standard answer to this problem.  You shoudl wash your hair whenever it is greasy.   Also if you work in a dusty or unclean environment then you should wash it every day.  Similarly if you smoke or work in a smoky environment your hair could probably benefit from regular shampooing.
If your hair is very dry then washing it too often may strip away some of the protective oils contained in the hair follicles.  However, sometimes if hair is not washed often enough and is dry it can go a little frizzy.
Some people wash their hair using water only and although they may have greasy and lanky hair for a little while, they assert that the natural ph balance of the hair is restored and shampoo is not needed.  But many people like the smell of freshly shampooed hair.
So, just wash your hair as often as feels right for you and this should be fine.

It depends on everything. If you get really greasy easily, then washing it everyday might not be so bad. Also, if you work in lets say a construction site, for example, then its also probably a good idea to clean it. However, if you don't get very greasy hair, and you work at a place where you arent going to get very dirty, well then maybe every other day wouldn't be too bad. It really all depends on what type of hair you hair, because if you wash your hair too much, then the natural oils in your hair aren't there, and you hair won't be as healthy, and shiny.