pieced together from various sources, the story of how to choose a new incarnation runs thus...
old monk dying, says... mmm, look for me in villiage X when I've gone...
a few years later, the monks left behind visit villiage X, with possessions of the dead monk, and present them to the village children... if the child "recognises" the objects, or if the child appears gifted, intellectually, they say- Oh! Here is our old dead monk in a new body... the alive-monks take more than one child, usually a small group, off to the monastery... they give all the kids instruction in buddhism, and fill their heads with stories about their last life, and the ones with the most aptitudes are chosen to be tulkus... reincarnations of others... these tulkus then are trained further, and the one with the most aptitude is usually selected to be the new dead-monk and the lesser kids his mates...
what a great system!
unfortunately... sometimes the children do not want to play ball... and who can blame them? You're not you- you don't exist! -you're a dead guy who has ousted the original soul which should have existed in this body with magic and you sealed up the womb door with special guhya tantra rituals! You are not samraja, son of Makunda- you're a Tulku who has existed for five hundred years...