To expand on an earlier answer, and what the OP himself mentions, I will add a few more elements.
First, the count of persons on the trip. The rescuers need to know when they are done. If they've found four people and five went on the trip, for example, that means they keep searching. Add notes of any relevant medical information about each person, such as diabetic, heart condition, mobility issues, and so on.
Next, a broad inventory of what equipment you have, to give some indication of how well prepared you are to aid your own survival and rescue. If you went out for what should have been a day hike without a tent and only a small lunch, for example, it might indicate a greater sense of urgency then if you went out for a week long trip with full kit.
Finally, it may be useful to provide a description of your vehicle(s), to include license plate numbers, and at what trail head you will be parked. As a former member of the U.S. Coast Guard Auxiliary, we would request this information when receiving a report of an overdue vessel, especially if the boat was launched from a trailer at a ramp. We would send someone by car to that ramp to look for the tow vehicle and trailer, to verify the boat had not been recovered at the ramp. Even for a boat at a marina, we might call that marina and ask if the owner's car was still in the parking lot. The same concept applies to an excursion in the woods instead of the waters. The rescuers will send someone to the trail head parking area to verify you have not returned to your vehicle.
For further guidance, here is a sample float plan from the USCGAux, and here is a similar form for hikers from Los Angeles County Sheriff Department.