Homeopathy is the only science on the earth with some fixed principles and theories which have never changed since discovery of homeopathy. One of the main principles is that homeopath need to select the remedy strictly on the basis symptoms of the patient, a medicine that will stimulate your organism to heal by itself.
A Homeopath needs to study personality trait of a patient and find a medicine from vast database of medicines which matches with personality of patient. But this is very laborious job and requires a lot of efforts and dedication on the part of the homeopath.
Also in homeopathy there are certain guidelines about how the case should progress in long run, which is called as DOC (Direction Of Cure). But some homeopath prescribes medicines haphazardly on the basis of pathology and fails to cure the case because the medicine is not selected on the basis of the laws of homeopathy (except some cases where luckily the medicine given is similimum of the case). In simple words, the homeopathic prescribing strictly following laws of homeopathy is called classical homeopathy, which has highest success rates.