as an opener try "how long have you had brown hair?",or, "have you had your hair cut"
one of the techniques i use is to remind students that the present perfect is used for achievements ("doctors have cured many diseases", "humankind has walked on the moon", "johhny has learnt to speak english very well")...
i try to tell students that the use of the auxiliary "to have" is important, to an english listener like myself, it lends to emotion such as achievement, or indeed, loss: "she has broken my heart"... it usually helps to know that the tense is very important in english, and if Ss grasp this they will become very good users of english. also, make sure they use the past participle correctly, drill regularly on this aspect.