The following 13 items should be included in your pack at all times in case of an emergency or if you are unexpectedly caught out overnight. You may not use all of the essentials on every trip, but they could keep you alive in an emergency.
1. MAP - A topographical map is the best type to carry. Learn how to use the map efficiently or it will add needless weight. Place it in a plastic zip lock bag and carry a pencil.
2. COMPASS - Generally, select a compass that will "settle" fast and has a straight edge. Know how to use your compass or it is useless weight.
3. FLASHLIGHT - Head lamps are most convenient but small bright flashlights are sufficient. Make sure you have fresh batteries in your light before you leave and pack enough extra batteries to last your trip. Many people carry an extra bulb as well.
4. KNIFE - Pocket knife, sharpened to your liking, with two good blades.
5. MATCHES - Wooden, strike anywhere matches, waterproofed and in a good waterproof container.
6. FIRE STARTER - Two 3 to 5 inch hard wax candles work well.
7. EXTRA CLOTHING - Bring an extra set of clothing suited to the worst possible conditions you could possibly encounter for the area and time you are visiting. Always include a stocking cap or balaclava.
8. EXTRA FOOD - High energy foods, such as Power Bars or hard candy.
9. WATER - One liter minimum.
10. FIRST AID KIT - There are many good first aid kits available commercially, or you could build one yourself. Carry it in a waterproof container.
11. SUNGLASSES& SUN BLOCK - Dark lenses with 100% UVA and UVB protection, or nearly so. Zinc oxide or sun block with SPF 15 or higher. Waterproof or "sweat proof" sun block recommended.
12. EMERGENCY SHELTER - A small plastic tarp or two large plastic garbage bags will keep the wind and rain off of you.
13. SIGNALING DEVICES - Many hikers carry a whistle and a mirror. Discarded CD disks make an adequate signaling mirror.