One important piece of information is your location. If you can download Google maps for the area you are in, you can consult a map even without cell or wi-fi service.
Many portable radios have a GPS feature than will give you a decimal lat and long. Know how to use it. Know what the information means.
I will second this. There are also Mapping Apps that work offline in a smart phone. They do need the GPS. You can download area maps of your trip, and then read the coordinates, or at least a road name and approximate distance to some town or other land mark.
As for using your radio, I would pre-load a set of frequencies you may encounter along the way. When you make your call, I would do it like this:
"Break, break, break. This is KX4XXX, my name is John Doe, and I have an emergency, can anyone assist me?"
When someone responds, say your call and name again, and tell them the type of emergency, the help needed, the number of injured, and your location the bast you can determine. Then, monitor that frequency or repeater, as the emergency dispatch may need further information.