[header] How to tell if someone might be offended by swearing [title] Consider whether or not you have ever heard them curse. [step] In considering whether this person is offended, reflect back on conversations you've had with them. Have you ever heard them curse before? Have they ever cursed in a text or over the phone? If they don't curse, then curse words could be offensive to them. 
[title] See what kind of music they listen to. [step] If you have the opportunity, notice what kinds of music they listen to.