The Shuriken Class

Actually Shuriken were mostly used as a nuisance weapon. They are supposed to distract the pursuers. Rarely will the shuriken really kill someone, unless you are a really lousy ninja. The idea is that if the shuriken strikes an arm or leg, it will prevent the poor ninja from wielding the katana properly. Constant practice makes the Shuriken instinctive to the Ninja, who could hit a dime at ranges up to 30 feet

Method 1: Hidden Method
There are many ways to throw the shuriken. I’ll bring you through some of these ways. One corny way is trying to hide the star in the hand so that it is hidden from the opponent's view.

This involves great skill because you can actually poke yourself in the palm while doing that and yelling OUCH loudly in front of your enemy will really make you look like Nar uto.

Method 2: The Fan
Another method that I’m sure you are familiar with is trying to throw more than one star at a time. The correct way is to throw them is in a spread-out pattern.

This method is great because you can scare your enemies as anyone who sees a barricade a missiles being launched at them will feel threatened. However, for a beginner this method rarely stabs someone, the best you can hope for is that the star hits your opponent on the head. Because the star is made of metal, you might even get an appreciative groan.

Method 3: Frisbee throw
The third style is to grip one point between thumb and forefinger and throw sideways with a quick springing motion, somewhat like a Frisbee. This method is great, because if it is a Frisbee, the Frisbee will definitely fly far and in an unpredictable motion. Except the shuriken is not a Frisbee. When you bend your arm to throw the star, try not to pock yourself in the chest. You opponent might just die - of laughter.

Judging Distances
It is very necessary that the star thrower learns to judge distances accurately. If you play the basketball you’ll know that ‘air balling’ will make you look terribly embarrassing.

The Stance
The stance will vary with the individual, but in general, the stance is the same in star throwing as it is in throwing any object at a target. Face the target in your natural throwing position with the left foot slightly ahead of the right.

Important: Do not throw the shuriken when jumping around. It is not as easy as it seems. If you really want to do that, try it on a target first.

Targets - Make or Buy Them
For out-of-doors practice (You will need them) you can either buy a target or make one. You may be surprise but targets can actually be bought. I guess it saves you the hassle of making one yourself. Even so, a good target can be fashioned from a 2-foot square of heavy board. I think soft pine boards are best. To make you work even harder, you can even paint Orochimaru’s face on it.

Source
http://www.narutofever.com/information/shuriken-and-targets/