If you are an employee of a firm, and you observe a strange face in your work environment or office, be kind enough to use this phrase by asking this question, “have you been helped or do you need assistance?”
Using the phrase, “have you been helped?” puts them at a confortable position to talk to you.
Do not ever catch yourself staring endlessly at a stranger in your office as though you are the police of the environment. It could just be that, the stranger is confused as to who to ask question or where to go. Courtesy demands that you be kind to visitors or strangers, by so doing you put them at ease. Correct?