sleeping through the night

I have 4 kiddos and so that means 4 times getting them to sleep through the night.
Before I can expect my kiddos to sleep through the night though I try from day one to get them on a *routine this may sound strict, but just like rules, routine is there to help life function more smooth. The routine is simple I feed my baby right when it wakes up then let it have awake time (as a new born that could be like 5 minuets) my 3 month old is awake right now for about1 hour. Then it is sleep time, and back to feeding them right when they wake up. So I get my babies on this routine as soon as I can it does take time like a few days of this consistent pattern and then they start to expect to be feed right when they wake up and for me it seems to make newborn life much nicer.
So now to get my babies sleeping through the night I watch to see when they are ready. Usually this is around 3 months.
I know they are ready because they do 90% of the work. They sleep longer and longer as the nights go by and they even sleep through the night on occasion. Now I know they are ready, and that they do not need to eat in the night I say need because, they may still want to eat but their bodies have already shown me they can sleep through the night and they just need help making it a habit.
This can be the tough part for everyone do not get them at night! let them cry it out. Now to do this you need to know that they can sleep through the night and if you are not sure you may want to check with your doctor to see if they are old enough.
This can be hard because they may not just go to sleep one night and every night after, they may wake up in the middle of the night out of habit and want to eat, and when you do not come they may cry and cry and cry, they may even cry for hours, usually it will not take more then a few nights of this, but if your child is really familiar with waking up at night it may take a long time to figure out the new routine.
I know this sounds bad let your baby cry and cry for night after night, but if your baby really is ready then it should not take more then a few nights for 3 of my 4 it only took 2 nights of crying it out, but my 4th (who is 3 now) took a few weeks it seemed like for ever, but we noticed before and notice still that she really latches on to routine. A good way to describe her is if you do something once she wants it to happen again and if you do the same thing more then once it is a habit so for her it made sense that she would take longer to sleep through the night we where asking her to go from waking up in the night for like 3 months and then expected her to just stop waking up at night at all, it was a hard habit to brake but we did she slept though the night eventually and is now growing strong finding new ways to challenge our parenting skills.

*There is a book that was so helpful to me when I had my first baby, and the things in it have helped with every child since that is where I learned about the routine I mentioned the bookis it is Secrets of the baby whisperer
it is a great book to have.