Build a fire.
No, not to make smoke signals silly, that would be stupid.
Take a thin piece of paper, write a note on it, make it into a whirly-gig and float it up into the sky on the thermal created by the fire--I'll get it eventually.
Whirly-gig instructions to follow:
Don't forget to write your note!
(just click on the Whirly-gig image)