Things You'll Need
Instructions
Start your practice on bars of soap. Soap has a lot of advantages over wood. It is soft enough to be manipulated by hand, yet hard enough that you can use it as a launching point before moving to wood. It will dull out your blade much more slowly, and the risk of injury is less because you don't have to put so much pressure behind your blade.
Once you've gained a steady hand and a basic ability to turn your ideas into sculptures, go out into the yard and find some large branches. These are best because they're free, and while they may not be as ideal as store-bought blocks of wood, it's always best to practice on something that won't hurt your wallet.
Go to your local wood craft store once you believe you are ready to take the next step in your hobby. The largest one nationally is Woodcrafters, and they sell all sorts of wooden blocks along with various carving tools to help you get the professional look that you want.
Keep safety your priority. Always use a knife that's sharp enough to cut through the wood without having to force it through. This also keeps you from chipping the wood, instead of cutting it. Make sure that you cut away from your hands, fingers, and body.
Have fun with it. Whittling is not a competition, it is a way for you to clear your mind and think for a second. Many people who whittle use it as a method to keep themselves busy enough to not be bored, but not so busy that they can't think. It should be a relaxing pastime, not another thing to stress you out.