The biggest stress on new parents (besides giving birth itself) is the lack of sleep. When babies are born, they are on a very short eat/sleep/poop cycle.  They will wake up to feed, poop, and sleep every couple of hours—through night and day.
I’ve been through this three times, and let me tell you the single best piece of advice I could say to you: sleep train your babies as soon as they’re ready.
Every child is different, but in general, they may be ready as early as four months old. We used the Ferber Method with all three kids and are happy with the results (the oldest child is now nine years old).
The Sleep-time Ritual
Go through the same sleep-time routine every time you put the baby down to sleep. These are the activities you perform every time before putting the baby to sleep. For us, it included feeding, turning on the same sleep song on the sound machine, setting the mobile into motion, washing up, change of diaper, applying lotion, wearing pajamas, and putting on the sleep sack. Sleep times should be the same every day.
Ferberization
Put the baby in the crib, whisper “good night,” and tip-toe out of the room, gently closing the door behind you. For the first 2-3 nights, the baby will probably start crying. Check on the baby after 3 minutes, then again after 5 minutes, then again after 10 minutes, then every 10 minutes after that until the baby stops crying and falls asleep.
It can be difficult hearing your child cry and not rushing in to soothe them. Fight that urge. Know that the baby is safe, and you are checking on them every few minutes to be sure they are safe.
Having a video baby monitor helps, as you can see your child even when you are not in the room with them. Giving the child a security item such as a pacifier or stuffed animal to hug may also help them calm down. You may still have to feed younger babies in the middle of the night.
Criticism and My Thoughts
There is some criticism that babies should not be left to cry because it may hurt their psychological development. Those are valid concerns worth considering. Every parent has different ideals, goals, and beliefs. There is no single correct way to raise your children, and the only bad parents are the ones without their children’s best interests in mind. I am only reporting here about what worked well for me, as a parent to three children.
The Ferber Method has been used for well over a century, and no evidence has emerged about any adverse effects. We didn’t sleep train our oldest child until she was about nine months old, and let me tell you we didn’t sleep much for those first nine months! We followed the Ferber Method for the next two children, and they both slept through the night by six months, and they still enjoy sleeping now. The second child stopped taking daily afternoon naps at around age 5. The third child, at age two, would wake in the morning in a good mood, happy to sit in the crib and play until someone came to get him.
If I had a fourth child, I would do it all over again.