Just a Call
If lucky enough and you have cellphone service, call for rescue. If you aware, let them know relatively where you are stranded and have them send help.
During the daylight hours, cover the fires with damp or wet leaves and branches. This will cause the fire to smoke. If accessible put some rubber into the fire to make the smoke black which is makes the smoke more noticable
If available, take anything that is shiny and reflective such as a mirror or belt buckle. With this reflector try to get to the highest part of the island. From there take the reflector and have the sun shine onto it. This will allow the sunlight to reflect back, and you can aim towards a passing ship or plane to call out for help.
Clothing, Rocks, Branches
With any or all of these objects you should create patterns like triangles, Xs, or circles. If you have enough objects spell out S-O-S, which is the international distress signal. Make sure these patterns stand out from the color of the ground and are large enough so a passing aircraft can see them.
Message in a Bottle
This isn't one of the best techniques but could help. Take a empty bottle, write a message, and throw it out into the water. Try including the best information about your location as you can.
In the Meanwhile
Getting rescued may take awhile so besides trying to get help, what you need to do is
- Stay calm
- Find water and food
- Make a shelter
- Have patience
- Have hope