1) Fire
Fire is the most important survival skill. It can provide warmth, purify water, cook food, signal rescuers, create light, and comfort and keep predators at a distance. Every person who heads off into the outdoors should have a dependable way of starting a fire. TIP: A few small fires provide more heat than one large fire.
2) Shelter
A shelter is how you protect your body from excess exposure to sun, cold, wind, rain, or snow. Clothing is your first line of shelter. The right clothes for the right environment is key. A simple lean-to style shelters are the most common depending on available resources. TIP: Always have a hat, this might be the only shelter for miles.
3) Food & Water
Food and water are literally vital to survival. If possible boil all water 10 minutes (add one minute for every 1000 feet above sea level). TIP: Never wait until you are without water to collect it.