An effective safety orientation program means you're remembering that you don't know what they don't know. To generalize, new employees are young and lack the knowledge and experience they need to jump in and work safely. You have to start somewhere and you can't take safety knowledge and the context of risk for granted. And because you don't know what they don't know, and what they don't know can hurt them, make sure safety orientation starts on day one and get everything on the table:
When something doesn't feel right or safe, speak up; nothing is more important than the wellbeing of the worker.
General site hazards.
Specific hazards involved in each task the employee may perform.
Safety policies and work rules, including incident-prevention strategies and injury-reporting procedures.
Location of emergency equipment like fire extinguishers, eye-wash stations, and first-aid supplies.
Steps to take following an incident or injury.
Proper reporting of emergencies, incidents, and near misses.
Selection, use, and care of personal protective equipment.
Emergency evacuation procedures, routes, and security systems.
Safe use of tools and equipment.
Safe lifting techniques and material-handling procedures.
Hazardous materials awareness and MSDS basics.
There are also employers who also like to include information about the costs associated with incidents. Some companies even choose to bring in an employee who has been injured to explain what happened and the effect of the injury on the employee and his or her family. Does it sound a bit too negative too soon? I can't answer that, but a first-hand account (and hearing about its aftermath) has its place.