Article: If you don't have a bow, then hit them with a sword and then quickly move backwards. If the creeper starts flashing and getting bigger, get away from it until it either stops or explodes. If you kill it, collect the experience and the item(s) it may drop, like gunpowder. When a creeper is hit by lightning, it has a bluish aura surrounding it. When it explodes, it is double the explosion potential compared to normal Creepers. You kill a charged creeper in the same way as a normal creeper.

What is a summary?
If you have a bow, use it to kill the creeper. Repeat. Note that there is also a charged creeper.