The Ancient Greeks used the spear mainly in the Phalanx. The spear was about 6-9meters in length with an iron tip on the front and back of the spear. The front was used to stab and rip through any enemy defenses whereas the back end of the spear was used to kill any fallen enemies that were at the feet of the Phalanx.
http://www.mlahanas.de/Greeks/WarTech.htm