Find out what age it's safe to let a baby 'cry it out' so that he'll (eventually!) sleep through the night. 

At what age can you let a baby "cry it out"? Is it harmful to let, say, a 3-month-old cry for a few minutes instead of rushing in to nurse or rock her back to sleep? While experts say there's no set age to begin sleep training, but it's best to wait until you're sure your baby no longer needs to eat in the middle of the night.

For most babies, this is after 4 months, but some may be ready sooner. It's probably best to start before 6 months, however; the process becomes more difficult after a baby can sit up by himself.

However, you should never just let your baby "cry it out" totally on his own. Instead, check in on him frequently to make sure he's all right. This will not only reassure and help calm your baby, but also ease your new-mom nerves. Once you decide that the time is right for sleep training, be sure to start with bedtime. Only after your child has learned to fall asleep at night—which usually takes about a week—should you incorporate this method during naps.