When stopped at an intersection with a stop sign, what should you do before proceeding?

Answer: A — Check traffic in all directions

When stopped at an intersection with a stop sign, it is important to first check traffic in all directions before proceeding. This ensures that the coast is clear and that you can safely proceed to cross or make a turn at the intersection. Waving your arms to other drivers (option B), honking your horn (option C), or flashing your headlights (option D) are not necessary and can even confuse other drivers. It is best to follow the standard practice of checking traffic in all directions before proceeding to ensure the safety of yourself and others on the road.