Prefacing questions with 请问
Before I want to ask a stranger, I will try to get their attention first.

Saying 您好/你好 (Hello/Hi) before starting my question, then 对不起打扰了,请问 or just 请问 (Excuse Me) and followed by the question.

您好,请问附近的医院是往哪个方向？ 
嘿，打扰了，请问附近的医院是往哪个方向？