I would initially recommend waxing every two - four weeks to begin with as your hair will grow back slightly quicker if you have previously been shaving or using depilatory creams. After a couple of waxing treatments you should start to notice the hair growth slowing down. This does depend on many factors such as age, sex, hair growth cycles and the area you are getting waxed.
The hair should be at least 1/4" long for a good wax.
Once you are in a routine you will start to notice that the hair growth will slow down and possibly become finer. The average time then for waxing would be between 3-6 weeks depending on your hair growth.
I use cream wax which is kinder to the skin leaving the skin feeling silky smooth after the treatment.