If you want to make your hair grow faster, then look for good days. If you want make it slower - look for bad days.
First rule is: if Moon is rising then the day is good, else - bad.
Second: if Moon in "Pisces" or "Cancer" it is bad for growing, but good for stop it.
Look to haircut calendar for all 2012 year. Click here
Want to know about current moon in specific place?
Please specify what city are you looking for.