Do you mean like a pointy stick or more like a javeline?
 
Either way just start out with a wooden spear until you get the form down (the spear shouldn't turn in flight). Just start with a 6 foot sapling, cut off at base make base end pointy, and you have a spear. Lenght is important if it's less than 5 ft ususally you will have problems getting great range or having it just have an unstable flight pattern.  
 
For throwing throw it like a football (american) try to get a spiral, but most important rember the turning part is your hips, your arm just throws striaght. If your arm throws on a round plane then your spera will also travel on a round plane and won't hit point first.  
 
Check out Cold Steel's Spears in Action video. Its online free, probably on YT. and it's probably close to 20min long explaining on how to use a spear for SD, throwing, and hunting. As well as some spear testing videos.
 
Be resonsible, remember these were used for war not to long ago and can be very effective weapons.