I have a travel tag and a home tag for each dog. They stay on the appropriate collar/harness.
The home tag has my cell phone number. The travel tag has my cell phone number AND the license plate number of my RV.
I also will use those old style "barrel" tags and put a slip of paper inside with the campground, site number, and days I am there. Just another way for folks to reconnect me with my dogs.
I also have the rabies tag and the license tag.
And yes, my dogs AlWAYS have a collar or harness on them. And if we are out of a fenced area, they are leashed.