Make.... Ninja stars??? Well, you could simply buy them in a Ninja village's Smith, but those do not exist anymore xD!! Though, if you want to make a hira shuriken yourself you should get four long nails, put them into a star shape and tie them together with a string. At this point, you should have your shuriken ready to pierce in someone's body xP
But mind you, you need to leave a space in the centre to make it balanced. Simply tie the strings without wrapping them on the centre ^^
If ]00 want other shurikens, go and buy them! xD!!!