The ever popular CIO sleeping method for babies was created by Dr. Richard Ferber. Essentially, it consists of "teaching" your baby (of normal weight, aprox 6 months old, no health problems or pains) how to sleep on his own. The magic consists on putting your awake baby in the crib and walking out of the room. He will cry. You let him cry it out for a few minutes, go in to reassure him (without picking him up). You leave. He cries. You wait for another set interval of time. Go in. Non cuddly reassurance. And so on until he passes out from crying. This means he has learned how to sleep on his own.
One of the ideas behind this is that if you comfort your child by picking him up and helping him calm down in the safety of your embrace you are actually rewarding his crying. Manipulative beasts that they are, babies will then fake distress and cry on purpose to get you to pick them up.
Ferber, though, in 2006 loosened up a little and amended his theory. Reading between the lines it seems, at least to me, that he isn't willing to backtrack on what he said and the eminence that he has become, but he is leaving parents a lot of wiggle room. His new bottom line is: you know your baby, what is right for him, what you need and what he needs. Figure it out, suckers. I know, he leaves us back at square one and the baby is still awake.