everyones hair grows a half inch every month, but what you can do to maintain healthy hair so you can see hair growth, is to trim regularly condition instead of washing every week, that way you are still washing the hair but you are also giving nutrients, sometimes shampoo can really be strong on the hair but if you really need to use shampoo like if you work out then by all means do so. also deep condition the hair with something that has protein you can also use leave in conditioners when you want to wet the hair for a wet style. try to stay away from heat like blow drying and opt for roller sets instead and minimize the use of the flat iron as much as you can those are my tips for longer hair
another thing is also massaging the scalp with the balls of your fingers so you are increasing blood flow to the hair follicle that in it self does the job they also do that process for free in most hair salons or hair spas