Check out the book SLEEPLESS IN AMERICA. It's not a "how do I get my baby to sleep alone in his own crib book" (that's Ferber - cry-it-out method), but it will help you a lot with regarding how much sleep a child needs and what would help your child feel comfortable at night.
Should you do the cry-it-out method? Depends on who you ask.... ask me and the answer is no. I don't think it's "good" for babies and toddlers to cry themselves to sleep (induces stress, high cortisol levels harms the brain - it kills brain cells). If any baby is so upset that they are throwing up, that's really not good.
Even Ferber updated his "recommendations" and backed away from some of the stuff he wrote. Here he admits to co-sleeping (woo hoo - a step for mankind and babykind!)
BUT I think there is a middle ground... yet I don't know HOW to do it gently.
I nursed my kids to sleep till they were 3 (that was a bit much, I know) and then lay with them till they conk out.
Though looking back I wish I nightweaned my 2nd child at 2 yrs because the nighttime nursing to sleep wasn't working well for me.
Essentially, MY middle ground is, they are not in our bed (family bed - hubby doesn't like being kicked at night - go figure - LOL), they are in their own bed, BUT I do lie with my youngest (she will be 5 in 2 weeks) to sleep. When she wakes up around 5 am, she quietly walks down a long haul, quietly knocks on the door and I quietly walk back (no arguing, no lectures, no punishments) and I cuddle back to sleep and stay there.
How perfect is that? Everyone gets their needs met. Hubby gets his need for sleep, young children get their need to feel save and loved at night and I feel no guilt and I know I'm doing the right thing.
My kids (9 yr old boy and 5 yr old girl) share a bedroom. He's in a twin bed and she's on a mattress on the floor next to his bed. She's been there since age 1. (They have never slept in a crib. They hated it.)
When she was born, DS was 4. He would insist on cuddling with us (me and baby) while I nursed her to sleep - when she was in her room. Of course it was uncomfortable, but I let it continue. Within a few months, he realized, "this is so uncomfortable, I'm going in my own bed, later!" And from that point on, I didn't "have to" cuddle with him to sleep. Woo hoo!!!!
While ALL of us would love the fantasy of putting a child down in a crib and walking away without doing any of the "work", I don't think we can or should. I have a friend (now in her late 50s) who was adopted as a 3 yr old child. She is Japanese. She has fond memories of being rocked in a chair and read to as her nighttime routine. Wouldn't just leaving her in a bed, blowing a kiss, and shutting the door be easier on the parents? Guess so, but consider the child's feelings.
I have a friend who did CIO (we have the same age kids) and she used to brag how easy it was to get her to sleep. Around age 1.5-2 her daughter wised up and realized, "Hey! I don't like this!!!" So the parents were forced to driver her around for naps (all I had to do was the "bad habit" of lie down and nurse my kid, or just lie down with her). Or her daughter would wake up at 5am and there was NO WAY to get her back to sleep, so one of the parents had to stay up. Yikes.
Nothing is perfect. You have to make concessions. Find what works for everyone, without the trauma. :)