I accept it is not easy, but try as many friend's saddles as poss. I belive some dealers have a selection of try out saddles. If not, then it's trial and error. That isn't as bad as it seems because you do get an idea of what shape/size suits.
What type of cycling do you do? That has a bearing on a suitable saddle and many will offer you the benefit of their experience which may, I stress may, help.