"Signaling" is just the information that your visible choices send to those around you, including strangers. That's why it's called "signaling" -- your choices are broadcasting an information signal about you to others.

To not signal, you must make choices that carry little or no information in the context in which they exist. If you make choices in a context in which they are abnormal (e.g., dressing very casually in a context that others can't access in similar clothing), they inherently broadcast unique information about you. In some cases, that information can create a complex side effect in how people perceive you, even if you don't intend it (e.g., "this person put in the absolute bare minimum effort, because they knew we'd have to be nice to them no matter what, which feels disrespectful to me; their lack of optional effort for others signals that they only care about themselves, not us").