Essentially, any knife can be thrown competition style. Obviously, you want a sturdy fixed blade for this - throwing is less stressful than some think, but for constant throwing you might want a specific heat treatment. Obviously, avoiding cheap models is a good idea - Cold Steel's True Flight Thrower is inexpensive and made of nice high carbon steel.
There are two type of throwing knives: those that throw from the blade and those that throw from the handle. Some knives are asymetrically balanced to accentuate one throw, while most knives are center balance and can be thrown either way.
In general, heavier knives are easier to throw.
If you want a reliable throw for any tool or knife, you can "snap" a pointed object into a target from a couple of meters away - the knife travels in a straight line into the target with no rotation. The physics of this motion are fairly intuitive, but hard for me to describe.
If you want to learn how to throw knives - be warned that it is not a useful skill - you can saw the end off some heavy nails to make throwing spikes.
I hope this helps. There are archived posts out there with more information. Please be responsible.
