One of the tasks you need to consider if you get lost or are injured and can not reach the trailhead, is a way to get attention of rescuers. Depending on the environment where you are stuck, you can signal for help in many different ways. It's a good idea to set up a few different ways, if you can.
Be sure to set up your signals in the most visible place available to you so they can be seen from as many directions as possible.
In some frontcountry hiking areas, cell phone reception is pretty good. The further from civilization you go, the less helpful a cell phone becomes. In the areas I hike, they seldom work so I never take one along.
In the United States, three of something signifies that help is needed. That could be three whistle blasts, three gun shots, three piles of dark wood on light sand, or three fires burning. The fires can be in a line or a triangle, but make sure they are pretty far apart and in an open area to be seen from overhead.
Reflecting the sun's light to distant places, such as an airplane or helicopter, can be very effective at getting attention. A mirror can reflect light miles across the open. If you can get to a high spot, you can spend time signaling to distant places on the horizon until you see an airplane flying. It's better to signal at a plane that is in the distance rather than one that is up above you since the pilot can't see straight down.
There are specially made signaling mirrors with a hole in the center for sighting. But, any shiny surface can work - a compass, watch, knife blade, ... are all possibilities.
Sight the reflection on the distant target and keep signaling it until you get a response, such as the plane dipping its wings or the helicopter circling overhead.
Once you have your survival fire going, gather more wood into an open area and lay a large fire ready to be lit. Also, gather dry leaves, pine needles, moss, green pine boughs, and a bottle of water. This will be your signal fire and you want it to be pretty big and as smoky as possible.