I think the basic features they look in a shaper initiate may be a clean background and ability to work hard. Then, the initiates are promoted to novices if they show a satisfactory progress in whatever they are learning. After that, the novices are promoted to apprintices if they manage to learn what little they are taught without raising doubts about the shaper-belifs or breaking too many rules. Finally, if they manage to successfully complete the mission they are assigned to, they are promoted to full shapers (which includes guardians and agents)