Final answer:
The primary responsibility of a security guard coming on duty is to receive a briefing from the outgoing guard, which includes important information and instructions for their shift.
Step-by-step explanation:
A security guard coming on duty must complete several tasks to ensure a smooth transition between shifts and the continued security of the property. One pivotal step is to receive a briefing from the guard they are relieving. This briefing should include any unusual events, particular instructions, or important information that the incoming guard needs to be aware of. While other steps like checking that the outgoing guard has safe transportation home and a complete patrol of the perimeter are beneficial practices, they are not the primary responsibility of the incoming guard during a shift change. The outgoing guard might also provide documentation like a shift report, which although useful, does not typically require multiple copies to be made by the incoming guard.