If you left your itinerary with a responsible adult, someone will be looking for you when you don't return. Help them find you by using the three basic types of signals: mirror, ground to air, and sound. A commercial signal mirror with a sighting hole is one of the best ways to attract the attention of overflying aircraft because it can be seen 50 miles away. Plastic mirrors don't work nearly as well. A CD-ROM disc makes a great makeshift signal mirror, plus it has a sighting hole. Go to an open area, preferably on a high point like a hilltop, and using the sighting hole, shine the reflected light in the pilot's face. (Use a tree or bluff, not a real plane, when practicing.)
You can also attract the attention of aircraft by laying your space blanket on the ground, reflective side up. Or make a big X on the ground (universal sign of distress) with gear or by digging an embankment in snow. A hot coal bed piled with green vegetation will make white smoke that's easier for rescuers to see. Three fires in a triangle can be seen from 30 miles away. Also, don't forget about sound signals. Sound out SOS by blowing three short, three long, then three short whistles. If rescuers are near, bang on pots and pans.