A survival knife can help save your life, but it can also cause you harm if you aren't careful using it. The most basic safety measure is to always cut away from your body. Keep your eyes on what you're doing, and keep a firm grip on the knife and whatever you're cutting so there are no slipups. You also want to make sure you don't run with a knife, try to grab a falling knife or leave a knife lying around unsheathed. Always use two hands if you're closing a folding knife.
Be extremely careful about using a knife if you're not focused on the task at hand. Hunger, thirst, cold and exhaustion can all be powerful distractions, so make sure you're up to performing whatever activity you're attempting. Otherwise, you could just end up making your situation more dire.
Since your survival knife is so incredibly useful, you'll want to take great care you don't damage or lose it. If you don't let it down in this respect, it's much less likely to let you down in return. Survival knives are built tough to undergo rigorous use, but some are less durable than others so it's usually best to avoid getting too creative when using them. For example, since these knives aren't meant to bend, they can break if you try to use them to pry things open. You also want to avoid using then as awls because this can damage the tip. Don't stick your knife into the ground and don't heat it unless it's essential.
Keep the knife clean, dry and sharp at all times. When you sharpen it, be careful to maintain the point and overall shape of the blade or it could weaken. Always make sure you put it away (ideally fastened to your belt) after you've finished using it, because otherwise you could break camp without grabbing it. Sheaths can be made of many materials like leather, metal, plastic or cloth. Whichever you choose, make sure it's reinforced and attaches firmly to your body. A hole for hanging it on a lanyard can be handy, too. Remember never to throw your knife either -- beyond possibly damaging it, this is also a good way to lose it.
One last good tip is to always buy a survival knife from someone knowledgeable in the field. It's worth the trip to a specialty store to know you have a knife that won't let you down, even in the face of dire circumstances. For more information that can help you out in a pinch, venture a look at the links on the following page.