Firstly, there is no right or wrong way to throw a knife or other pointed object.  If you can throw it accurately, comfortably and with minimum effort then chances are you have found your style.  If you haven’t then perhaps you’ll find an option here that will make it easy for you to do so.

A lot of throwers use the Side Pinch. It seems to be an instinctive grip. Always try to hold the knife at exactly the same point of the knife for every throw. If not then you will be throwing at various lengths of knife. This will affect your performance.

The Thumb On Top is a difficult grip to master from the start. But quite a few top throwers use this style and maintain that you can get a lot more accuracy from it.  [But they're wrong. - thunkjunkie].

This is the bouquet grip. So called because it is like holding a bouquet of flowers. With this grip you can positively hold the knife and provide a smooth follow through. But you are shortening the spin of the knife as you are holding a lot more of it in your hand, compared with the two above. You may have to stand slightly forward to compensate for this.

This is used for the underhand throw, as opposed to the overhand throw for the three grips above. The knife is held horizontal to the target and is allowed to flow out of the hand, like loosing a ball underhand. This grip is good for some fun and fine tuning of your release of the knife. Don’t expect a lot of power from this grip. If you time your release and power right you can make half spins some distance from the target.

This is called choking the mon..I mean..knife. You are actually altering where you hold the knife and this alters the length of the knife, when it is thrown. [thunkjunkie: I think it has more to do with slowing down the spin than changing the length of the knife: long knife would usually mean 'stand further back'; short knife = 'stand closer'.]

This is the Military Throw, so called because it is to be used with bayonets, which usually have one side sharpened. With practice the half spin distance, with this grip, can easily(?) be extended to 20′. By releasing far earlier than usual, ie behind your head with an overhand throw, you can control the spin of the bayonet and slow it right down.

The same grips can be used when thrown by the handle (except the Military). It’s worth experimenting with all of these. When you find the one that seems natural to you, stick with it! [I can only presume that the pun is intended].