The Stalfos is the miniboss guarding the Mirror Shield in the Earth Temple. it should be noted that is is possible to skip this miniboss. However if you run out of magic you'll be forced to at least fight the first Sstalfos of the three.
For any Stalfos in this game, the strategy is always the same. Place down a bomb near their feet and wait for it to blow them up (if you're lucky the Stalfos will try to hit you and blow up the bomb early). Then target the head of the Stalfos and use the boomerang to stun it in place. Now pull out the skull hammer and do a jump attack on the head to finish it off.