One needs to tread very carefully, lest he teach Torah to a goy, which is forbidden. [E.g., at work – if asked about something Jewish]
Another example is when hinting to a goy to do something on Shabbos, you have to know how to do it the right way, without teaching Torah to the goy and without transgressing the issur of amira l’akum.
Lights are on in bedroom.
Me to goy on Shabbos: “Excuse me, sir. It is hard for me to sleep when the light is on.”
Goy: Why don’t you turn it off?
Me: Today is the Sabbath.
Goy: Would you like me to turn it off for you, then?
Me: I am not permitted to ask you to do that.
Goy: So what do you want from me?