You might also know this technique by it's actual name: Ferberizing.

Named after Dr. Richard Ferber, the gist of the method is this: if you put your baby in the crib and leave them alone, they'll cry -- but not forever -- and then they'll fall asleep. Eventually, they learn how to soothe themselves to sleep.

How to Do It
When your baby is around 4-6 months old, they are old enough to learn and benefit from a routine.

Create a bedtime routine that works for your family. Pick a bedtime, and 2 or 3 things to do with your baby before bedtime. Some ideas: give him a bath, read the same story, sing the same song, play the same (quiet) game. You get the idea.

Then, while your baby is still awake, put him in bed. Pat and comfort your baby as he tosses and turns in his crib, but don't pick him up or give him a bottle. Then, leave the room.

Here's the hard part: he'll cry. He'll probably scream his head off. In rare cases, he may even make himself sick. But your reaction should be the same – pat and comfort him while he's still in his crib, and don't pick him up or feed him. (Of course, clean him up if he gets sick!)

But here's the twist. Check on him in regular intervals. You should decide what amount of time between check-ins feels right to you. Maybe you'll check in every 5 minutes. Maybe it's every 15 minutes. But then you should leave the room again. Over the course of the week, increase the amount of time between check-ins. Ferber calls this "progressive waiting."

In about a week, your baby will recognize his bedtime routine, he will have learned that crying won't get him out of his crib, and he will have learned how to fall asleep by himself.

Of course, you are free to modify this basic premise. Maybe you want to stretch the routine over 2 weeks instead of one. And think about what you would do if your routine changes. If you're on vacation or if someone is babysitting, for example, you'll have to be flexible.

The point is for your baby and you to both start getting a good night's sleep, with as little drama as possible.

The Controversy
Dr. Ferber introduced this sleep method (among others) in his 1985 book. Solve Your Child's Sleep Problems. Since then, his critics have labeled his technique as a "cry-it-out" solution. Their charge: it's needlessly harsh on such a young child, and in fact, can leave emotional scars.

Ultimately, you know what works for your family, and what doesn't. No one likes to think that they are putting their child under undue stress, but Dr. Ferber's answer to this would be that his method, when practiced correctly, is actually designed to avoid unnecessary crying.