Unlike magic, prayer does not require runes to cast, and they are all personal spells(they also, unfortunately, do not give you XP when you cast a prayer like magic does). Instead, they use the Prayer stat. Each spell has a Drain stat - this is the rate at which your Prayer points go down. The higher the number, the faster they drain. The only way to regain Prayer points is to recharge them all at once by going to an altar and praying. You can build your Prayer score by burying regular bones, bat bones, big bones or dragon bones. You can also mine some silver to make a Holy Symbol of Saradomin, which raises Equipment Prayer by 8 points. You must get it blessed by Brother Jared in the Cleric's Guild, and to do that you need 31 prayer. The Cleric's guild is on the second story of the Monastery.
Below is a list of all the bones and the experience each gives for burying them.

Picture	Bone	XP
	Bones	3.75
	Bat Bones	5
	Big Bones	12.5
	Dragon Bones	60

Below is a table of each Prayer, it's Drain Rate and what level you need to be to use it.