What are the precautions that should be taken when verifying the laws of reflection?
The best way to demonstrate the laws of reflection involves a narrow, bright beam of light to shine on reflective surfaces; for this a laser works very nicely. But lasers can be hazardous; even if they are not powerful enough to cause burns or damage anything (and it would be foolish to use such a powerful laser for this demonstration), they are usually still bright enough to cause eye injuries.
Thus, if you're going to do this demonstration, it is important to make sure that no one ever looks directly into a laser or shines a laser directly into someone else's eyes. Beyond that, demonstrating the laws of reflection is relatively safe and straightforward: Shine the laser at reflective surfaces at known angles and measure the angle at which it reflects.